Evaluation of pregnancy outcomes in mothers with COVID-19 infection: a systematic review and meta-analysis

Abstract

Pregnant women are one of the endangered groups who need special attention in the COVID-19 epidemic. We conducted a systematic review and summarised the studies that reported adverse pregnancy outcomes in pregnant women with COVID-19 infection. A literature search was performed in PubMed and Scopus up to 1 September 2022, for retrieving original articles published in the English language assessing the association between COVID-19 infection and adverse pregnancy outcomes. Finally, in this review study, of 1790 articles obtained in the initial search, 141 eligible studies including 1,843,278 pregnant women were reviewed. We also performed a meta-analysis of a total of 74 cohort and case-control studies. In this meta-analysis, both fixed and random effect models were used. Publication bias was also assessed by Egger’s test and the trim and fill method was conducted in case of a significant result, to adjust the bias. The result of the meta-analysis showed that the pooled prevalence of preterm delivery, maternal mortality, NICU admission and neonatal death in the group with COVID-19 infection was significantly more than those without COVID-19 infection (p<.01). A meta-regression was conducted using the income level of countries. COVID-19 infection during pregnancy may cause adverse pregnancy outcomes including of preterm delivery, maternal mortality, NICU admission and neonatal death. Pregnancy loss and SARS-CoV2 positive neonates in Lower middle income are higher than in High income. Vertical transmission from mother to foetus may occur, but its immediate and long-term effects on the newborn are unclear.

Keywords:

• Coronavirus
• COVID-19
• pregnancy outcomes
• SARS-CoV-2
• systematic review
• meta-analysis

Introduction

Severe acute respiratory syndrome caused by COVID-19 (SARS-CoV-2) is an emerging and rapidly evolving situation and a global public health emergency and crisis that can cause severe lung disease and death (World Health Organization 2020). The spread of this virus has caused a devastating epidemic, challenged health and social services and led to high mortality rates that vary according to the epidemiological and social characteristics of each country (Mascarenhas et al. 2020). Despite efforts to control the pathogen, COVID-19 was considered a pandemic by the WHO on 11 March 2020 (Silva et al. 2020).

Clinical manifestations of this disease range from asymptomatic cases and mild upper airway infection to severe and fatal cases with pneumonia and acute respiratory failure (Lopes de Sousa et al. 2020). Studies to date have shown that the clinical, radiological and laboratory features of COVID-19 pneumonia in pregnant women are similar to those reported in non-pregnant patients (Chen et al. 2020, Yu et al. 2020).

Pregnant women are a high-risk population for infectious respiratory diseases. This may be due to physiological and anatomical changes, such as an increase in the transverse diameter of the chest, diaphragm elevation, decreased lung capacity and functional residual volumes, increased heart rate and oxygen consumption, respiratory tract mucosa oedema, and increased secretions in the upper respiratory tract following vasodilation (O'Day 1997, Ramsey and Ramin 2001, Mosby et al. 2011, Mertz et al. 2013, Chen et al. 2020, Liu et al. 2020a, 2020c). These alterations may increase the risk of more severe disease compared with no pregnant adults. In addition to these mechanical changes, immunological adaptation is essential to ensure maternal tolerance to the foetus, which makes pregnant women a more vulnerable group (Silva et al. 2020). The first and third trimesters of pregnancy can be considered periods of increased inflammatory activity, while the second trimester is a period of decreased overall immune system activity (Mor et al. 2017, Liu et al. 2020b). Changes in cell-mediated immunity lead to increased susceptibility of pregnant women to being infected with intracellular organisms such as viruses (Zaigham and Andersson 2020).

Considering the importance of pregnancy outcomes, it is essential to obtain knowledge about pregnancy outcomes during the COVID-19 epidemic, including the severity of symptoms in pregnant women, possible complications during pregnancy, the possibility of vertical transmission, and the condition of infected infants.

In this way, healthcare workers can be adequately equipped with knowledge about the prognoses and management of pregnant women with COVID-19. Although studies on pregnancy outcomes in COVID-19 are increasing, most of them are case reports or case series with small population samples and conflicting results and the majority of cohort studies have focussed on evaluating the effects of COVID-19 on the general population. Additionally, there is a wide variation in the methodology and data reporting in recently published articles, making accurate data interpretation difficult.

The aim of this study was to conduct a systematic review and meta-analysis of the published literature on pregnancy with COVID-19 to evaluate the effect of this novel infection on maternal, perinatal and neonatal outcomes.

Methods

The present systematic review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) (Moher et al. 2009). This study was approved by the Research Ethics Committees of Vice-Chancellor in Research Affairs-Shahid Beheshti University of Medical Sciences (approval code: IR.SBMU.RETECH.REC.1399.760); and the study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) (code: CRD42022360777). The PICO question of this study was: in pregnant women with COVID-19 infection, what are adverse pregnancy outcomes, compared to those without COVID-19?

Search strategy

An electronic literature search was conducted independently by two authors, who were familiar with search methods and information sources, without any restrictions, in the PubMed (including Medline) and Scopus databases for retrieving original articles published in English language assessing the association between COVID-19 infection and adverse pregnancy outcomes up to 1 September 2022. Furthermore, to maximise the identification of eligible studies, reference lists of relevant articles and reviews included were manually evaluated as well. The following keywords, either alone or in combination, were used for the search: (‘coronavirus’ OR ‘COVID-19’ OR ‘SARS-CoV-2’ OR ‘SARS-2’ OR ‘2019-nCoV’ OR ‘2019 novel coronavirus’) AND (‘pregnancy’ OR ‘pregnant women’ OR ‘maternal’ OR ‘gestational’) AND (‘adverse pregnancy outcomes’ OR ‘pregnancy outcomes’ OR ‘pregnancy complications’ OR ‘neonatal outcomes’ OR ‘abortion’ OR ‘miscarriage’ OR ‘pregnancy loss’ OR ‘fetal death’ OR ‘stillbirth’ OR ‘preeclampsia’ OR ‘gestational hypertension’ OR ‘pregnancy-induced hypertension’ OR ‘PIH’ OR ‘gestational diabetes’ OR ‘GDM’ OR ‘hemorrhage’ OR ‘postpartum hemorrhage’ OR ‘PPH’ OR ‘Placenta abruption’ OR ‘placenta previa’ OR ‘preterm’ OR ‘premature rupture of membrane’ OR ‘PROM’ OR ‘Intrauterine growth restriction’ OR ‘IUGR’ OR ‘small for gestational age’ OR ‘SGA’ OR ‘Low birth weight’ OR ‘LBW’ OR ‘oligohydramnios’ OR ‘Apgar’ OR ‘fetal distress’ OR ‘SARS-CoV-2 infection of the neonate’ OR ‘neonatal distress’ OR ‘RDS’ OR ‘neonatal death’ OR ‘neonatal mortality’ OR ‘neonatal admission’ OR ‘NICU admission’ OR ‘malformation’ OR ‘anomalies’). Table S1 shows search strategy of the study.

Selection criteria, study selection and data extraction

In this systematic review and meta-analysis, all the studies with an observational design including case-series, cross-sectional, case-control, and prospective or retrospective cohort studies were included.

Studies were included if they met the following criteria: (1) the study population included pregnant women who had COVID-19 infection confirmed by positive viral SARS-CoV-2 RNA testing; (2) the outcome of interest was at least one adverse pregnancy outcome.

We also excluded non-original studies including guidelines, review articles, case reports, animal studies, studies performed in vitro, commentaries, editorials, correspondences, letters to the editor, meeting abstracts, as well as studies that did not provide accurate and clear data.

After removing duplicates recognised in databases and reference lists, titles and abstracts were screened to evaluate the suitability of the manuscript based on the final eligibility criteria.

The first assessment, carried out by three investigators (SN, MS and ASh). Disagreements were resolved through scientific discussions. The general characteristics of the studies, including the first author’s name, article title, journal name, country of study, publication year, study design, sample size, population characteristics and pregnancy outcomes were extracted from the studies and assessed. To prevent extraction and data entry errors, a control check between the final data used in the systematic review and the original publications was conducted by all authors.

Quality assessment

All studies included in the present systematic review were critically appraised for the quality of their methodological and the presented results. Three reviewers, blinded to study author, journal name and institution, evaluated the quality of the studies independently using the Critical Appraisal Checklist recommended by the Joanna Briggs Institute for a variety of studies (cohort, case-control, cross-sectional and case series studies) (Munn et al. 2019), and disagreements were resolved by consensus. The Joanna Briggs Institute Critical Appraisal tools included eight questions for cross-sectional and case series studies, nine questions for reporting prevalence data, 10 questions for case-control studies and 11 questions for cohort studies, that reviewers addressed for each study. The answer ‘yes’ to each question received one point. Thus, the final scores for each study could range from 0 to 8, 0 to 9, 0 to 10 and 0 to 11 for cross-sectional and case series studies, reporting prevalence data, case-control studies and cohort studies, respectively. Table S2 shows results of quality assessment of included studies.

Outcome measures in meta-analysis

Maternal, neonatal and foetal outcomes of interest were categorised into 10 outcomes, including five composite outcomes including: (1) preterm delivery was defined as birth below 37 weeks of gestation (preterm <34 weeks, and <37 weeks), (2) pregnancy loss was defined as death of an unborn baby (foetus) at any time during pregnancy (abortion, foetal death, foetal loss, still birth), (3) PROM was defined as rupture (breaking open) of the membranes (amniotic sac) before labour begins (PROM and PPROM), (4) IUGR/SGA was described a foetus that has not reached its growth potential (IUGR) and/or an infant whose birth weight was below the 10th percentile for the appropriate gestational age (SGA), (5) hypertension disorders of pregnancy (PIH, preeclampsia and severe preeclampsia, eclampsia), (6) GDM was defined as any degree of glucose intolerance with onset or first recognition during pregnancy, (7) maternal mortality was defined as the death of a woman from direct or indirect obstetric causes, (8) LBW defined an infant born weighing 2500 g or less, (9) NICU admission was defined as the admission of a Neonatal Intensive Care Unit and (10) neonatal death was defined as the death of a live born infant, regardless of gestational age at birth, within the first 28 completed days of life.

Statistical analysis

This study was conducted to estimate the pooled prevalence of pregnancy adverse outcomes in COVID-19 infected mothers. In addition, we compared the prevalence of outcomes with the control groups in case of data availability. The ‘Meta-prop’ using the Mantel–Haenszel method was applied to estimate the prevalence of outcomes in each group. The heterogeneity was assessed using I-squared statistics considering the threshold of 50% and the p value less than .05 for the significance of the related test. In this regard, we selected the random effect model if the data heterogeneity was confirmed. For the other situations, the fixed effect model was chosen. The difference between subgroups was explored using Chi-squared statistics at the significant level of .05.

We explored the publication bias using the graphical approach funnel plot and Egger’s test. In case of a p value less than .05 for the Egger test, we applied the trim and filled method. The forest plots for all outcomes pooled prevalence were depicted. All these plots included the study-specific data and the random and fixed effect pooled prevalence.

A meta-regression approach was used to explore the impact of geographical and economic variations on the outcomes. In this manner, the prevalence regresses on the income level of countries. The countries were classified as high income, lower middle income or upper middle income using income level of countries according to the World Bank classification (Bank 2021).

All the analysis and graphical presentations were done in R statistical software version 4.0.5 (R Foundation for Statistical Computing, Vienna, Austria) and the ‘meta’ library in this environment. All the confidence intervals were reported at 95%, and the tests were considered significant if the p value was calculated as less than .05.

Results

Search results and study selection

As the flowchart of the literature search in Figure 1 shows, the search strategy yielded 1790 potentially relevant articles. Based on selection inclusion criteria, 213 articles were identified for further full-text assessment. We included 141 studies, which included data from 1,843,278 pregnant women for this systematic review.

Figure 1. Flowchart of the literature search for the systematic review.

Out of 141 studies included, seven were case-control, 28 were case series, 26 were cross-sectional and 80 were cohort studies. Finally, a total of 74 including 69 cohort and five case-control studies were included in this meta-analysis. Table 1 shows the characteristics of cohort and case-control studies included in the meta-analysis.

Table 1. Characteristics of cohort and case-control studies included in the meta-analysis.

First author	Title	Country	Study design	Sample size	Feto-maternal outcomes	Neonatal outcomes
1. Manas Kumar Nayak	Neonatal outcomes of pregnant women with COVID-19 in a developing country setup	India	Cohort	162 mothers and 165 neonates	PROM: 25 (15.4%); meconium-stained liquor: 39 (24.07%); PPH: 2 (1.2%); maternal mortality: 1 (0.6%); preterm (<37 weeks): 27 (16.6%); late preterm (34–36 + 6): 17 (10.3%); very preterm (28–33 + 6): 9 (5.4%); extreme preterm (<28 weeks): 1 (0.6%); stillbirth: 2 (5.2)	LBW: 49 (29.7%); prematurity (<37 weeks): 27 (71%); RDS: 8 (21%); hypoglycaemia: 4 (10.5%); hyperbilirubinemia requiring phototherapy: 15 (39.5%); necrotising enterocolitis: 1 (2.6%); hypoxic ischemic Encephalopathy (grade II or III): 6 (15.8%); NICU admission: 38 (23%); mortality (<28 days): 5 (13.2%), SARS-CoV2 positive neonates: 3/32 (9.4%)
2. Madalina Timircan	Exploring pregnancy outcomes associated with SARS-CoV-2 infection	Romania	Cohort	101+ vs. 938–	PIH: 6 (6%) vs. 28 (3%); preeclampsia: 2 (2%) vs. 19 (2%); GDM: 5 (5%) vs. 66 (7%); PROM: 11 (11%) vs. 55 (6%), *p = .049	Prematurity: 15 (15%) vs. 75 (8%), *p < .001; ICU admission: 6 (6%) vs. 27 (3%); foetal malformations: 2 (2%) vs. 19 (2%); neonatal sepsis: 5 (5%) vs. 56 (6%); neonatal death: 1 (1%) vs. 4 (0.5%); SARS-CoV-2 infection: 2 (2%)
3. Jean Y. Ko	Adverse pregnancy outcomes, maternal complications and severe illness among US delivery hospitalisations with and without a coronavirus disease 2019 (COVID-19) diagnosis	USA	Cohort	6550+ vs. 482,921–	GDM: 706 (10.8%) vs. 44,554 (9.2%), *p < .0001; PIH: 350 (5.3%) vs. 31,787 (6.6%), *p < .0001; pre-eclampsia/eclampsia: 616 (9.4%) 33,078 (6.8%), *p < .0001; preterm labour with preterm delivery: 315 (4.8%) vs. 17,392 (3.6%), RR (95% CI): 1.3 (1.2–1.5); stillbirth: 63 (1.0%) vs. 3439 (0.7%), RR (95% CI): 1.4 (1.1–1.7); maternal mortality: 9 (0.1%) vs. 32 (0.0%), RR (95% CI): 20.7 (9.9–43.4)
4. Maria de Lourdes Benamor Teixeira	Maternal and neonatal outcomes of SARS-Cov-2 infection in a cohort of pregnant women with comorbid disorders	Brazil	Cohort	33+ vs. 82–	Preeclampsia: 2 (6.9%) vs. 13 (17.1%); preterm delivery: 7 (26.9%) vs. 10 (13.7%)
5. Masoumeh Abedzadeh- Kalahroudi	Maternal and neonatal outcomes of pregnant patients with COVID-19: a prospective cohort study	Iran	Cohort	56+ vs. 94–	Pre-eclampsia: 11 (19.8%) vs. 7 (7.4%), *p = .037; preterm: 19 (34.5%) vs. 12 (12.8%), *p = .003; PROM: 4 (7.3%) vs. 9 (9.6%); foetal distress: 9 (16.1%) vs. 4 (4.3%), *p = .016	LBW: 11 (20%) vs. 14 (14.9%); foetal or neonatal death: 2 (3.6%) vs. 0 (0%); NICU admission: 9 (16.4%) vs. 20 (21.3%)
6. Federica Di Guardo	Poor maternal–neonatal outcomes in pregnant patients with confirmed SARS-Cov-2 infection: analysis of 145 cases	Italy	Cohort	145	Preterm birth: 55 (38%); maternal mortality: 7 (5%)	Neonatal death: 9 (6%); vertical transmission: 7 (5%)
7. Mikael Norman	Association of maternal SARS-CoV-2 infection in pregnancy with neonatal outcomes	Sweden	Cohort	2323+ vs. 84,719–	GDM: 163 (7.0%) vs. 4331 (5.0%); preterm infants: 205/2323 (8.8%) vs. 4719/85,836 (5.5%); post term: 6/39 (15.4%) vs. 146/2042 (7.1%)	Admission for neonatal care: 271 (11.7%) vs. 7351 (8.4%); neonatal respiratory disorder: 2.8% vs. 2.0%; hyperbilirubinemia: 3.6% vs. 2.5%; mortality: 0.30% vs. 0.12%; hypoxic-ischemic encephalopathy stage 2–3 d: 3 (0.1%) vs. 82 (0.1%); neonatal convulsions: 6 (0.3%) vs. 173 (0.2%); severe brain injury: 1/38 (2.6%) vs. 45/675 (6.7%); RDS: 29 (1.2%) vs. 508 (0.5%); meconium aspiration: 3 (0.1%) vs. 117 (0.1%); SGA: 54 (2.4%) vs. 1864 (2.2%) LGA: 84 (3.7%) vs. 3144 (3.7%); SARS-CoV-2-positive: 21 (0.90%)
8. Sara Cruz Melguizo	Pregnancy outcomes and SARS-CoV-2 infection: the Spanish Obstetric Emergency Group Study	Spain	Cohort	1347+ vs. 1607–	GDM: 97/1309 (7.4%) vs. 136/1584 (8.6%); IUGR: 48/1290 (3.7%) vs. 44/1566 (2.8%); PIH: 50 (3.7%) vs. 55 (3.4%); threatened abortion: 41/1275 (3.2%) vs. 43/1545 (2.8%); PROM: 209 (15.5%) vs. 179 (11.1%), *p < .001; PPROM: 37 (2.8%) vs. 23 (1.4%), *p = .012; preterm: 149 (11.1%) vs. 94 (5.8%), *p < .001; abruptio placentae: 12 (0.9%) vs. 7 (0.4%); PPH: 61 (4.5%) vs. 86 (5.4%); severe pre-eclampsia: 28/69 (40.6%) vs. 10/64 (15.6%), *p = .001; moderate pre-eclampsia: 41/69 (59.4%) vs. 54/64 (84.4%), *p = .001; stillbirth: 10 (0.7%) vs. 3 (0.2%), *p = .023	Apgar 5 score <7: 20/1335 (1.5%) vs. 21/1597 (1.3%); NICU admission: 137 (10.2%) vs. 39 (2.4%), *p < .001; neonatal mortality: 6 (0.4%) vs. 2 (0.1)
9. Haley A. Steffen	SARS-CoV-2 infection during pregnancy in a rural Midwest all-delivery cohort and associated maternal and neonatal outcomes	USA_Iowa	Cohort	61+ vs. 939– (neonate: 65+/971–)	Diabetes (T1DM, T2DM, gestational): 8 (13.7%) vs. 147 (15.6%); PIH: 4 (6.6%) vs. 94 (10%); preeclampsia without severe features: 3 (4.9%) vs. 35 (3.7%); preeclampsia with severe features: 6 (9.8%) vs. 49 (5.2%); eclampsia: 0 vs. 1 (0.11%); PROM: 6 (9.8%) vs. 84 (8.9%); preterm labour: 3 (4.9%) vs. 74 (7.9%); antenatal hypertensive disease: 14 (23.0%) vs. 228 (24.3%); placental abruption: 1 (1.6%) vs. 20 (2.1%); chorioamnionitis: 2 (6.3%) vs. 30 (5.2%); morbidly adherent placenta: 0 vs. 1 (0.2%); pyelonephritis: 1 (1.6%) vs. 5 (0.5%); PPH: 14 (23%) vs. 153 (16.3%)	Malformations: 10 (15.4%) vs. 117 (12.1%); absence of live birth: 3 (4.6%) vs. 12 (1.2%); neonatal death: 0 vs. 10 (1%)
10. Asimenia Angelidou	Association of maternal perinatal SARS-CoV-2 infection with neonatal outcomes during the COVID-19 pandemic in Massachusetts	USA_ Massachusetts	Cohort	250/255 neonate	Preterm birth (<32 weeks) or VLBW (<1500 g): 6 (2.4%); preterm birth (<37 weeks) or LBW (<2500 g): 62 (24.3%)	SGA: 13 (5.1%); very preterm birth (<32 weeks) or VLBW (<1500 g): 6 (2.4%); preterm birth (<37 weeks) or LBW (<2500 g): 62 (24.3%); congenital anomalies: 12 (4.7%); hypoglycaemia: 14 (5.5%); encephalopathy: 4 (1.6%); SARS-CoV-2 positive: 5 (2.0%)
11. Sahar H Abdulghani	Consequences of SARS-CoV-2 disease on maternal, perinatal and neonatal outcomes: a retrospective observational cohort study	Saudi Arabia	Cohort	62 (48 asymptomatic/14 symptomatic)	Meconium-stained amniotic fluid: 10	LBW: 7; premature infants: 11; positive naso-pharyngeal swab: 1
12. Qingqing Luo	Characteristics and pregnancy outcomes of asymptomatic and symptomatic women with COVID-19: lessons from hospitals in Wuhan	China	Cohort	42 (16 asymptomatic/25 symptomatic)	PROM: 6; GDM: 4; PIH: 3; oligohydramnios: 2; polyhydramnios: 1; malpresentation: 1; placenta previa: 1; intrahepatic cholestasis of pregnancy: 1; postpartum fever: 5; premature delivery: 9	Positive nucleic acid testing of SARS-CoV-2: 1
13. Zahra Akbarian-Rad	Neonatal outcomes in pregnant women infected with COVID-19 in Babol, North of Iran: a retrospective study with short-term follow-up	Iran	Cohort	8	Preterm: 3	LBW: 1; need for resuscitation at birth: 1; respiratory distress: 2; feeding problem: 2; poor reflexes: 2
14. Chrissy Liu	Effect of SARS-CoV-2 infection on pregnancy outcomes in an inner-city Black patient population	USA	Cohort	56+ vs. 279–	PIH or preeclampsia: 8 (14.3%) vs. 34 (12.2%); GDM: 6 (10.7%) vs. 41 (14.7%); preterm 34 to 36 + 6 weeks: 5 (8.9%) vs. 24 (8.8%); early preterm < 34 weeks: 3 (5.4%) vs. 17 (6.2%); PPH ≥ 1000 cm^3: 7 (13.7%) vs. 36 (14.5%);
15. Mehmet Ozsurmeli	Clinical characteristics, maternal and neonatal outcomes of pregnant women with SARS-CoV-2 infection in Turkey	Turkey	Cohort	24	Maternal mortality: 1	NICU admission: 1; neonatal death: 1
16. Sindy C Moreno	Vertical transmission of COVID-19 to the neonate	USA	Cohort	19/21 newborn	Preterm delivery: 8 (38.1%); ≤34 weeks.: 2 (25%) ≤37 weeks: 6 (75%)	NICU admission: 13 (61.9%); TTN: 6 (28.6%); RDS: 1 (4.8%)
17. Mehmet Yekta Oncel	A multicenter study on epidemiological and clinical characteristics of 125 newborns born to women infected with COVID-19 by Turkish Neonatal Society	Turkey	Cohort	125	GDM: 7 (5.8%); preeclampsia: 6 (4.9%); hypertension: 2 (1.6) placenta previa: 1 (0.8%); maternal mortality: 6 (4.8%);	Prematurity: 33 (26.4%); LBW: 16 (12.8%); NICU admission: 108 (86.4%); neonatal mortality: 1 (0.8%); positive RT-PCR test: 4/12 (3.3%)
18. Citra NZ Mattar	Pregnancy outcomes in COVID-19: a prospective cohort study in Singapore	Singapore	Cohort	16	Spontaneous miscarriages: 2
19. Monica Cruz-Lemini	Obstetric outcomes of SARS-CoV-2 infection in asymptomatic pregnant women	Spain	Cohort	174+ vs. 430–	Threatened abortion: 9 (5.2%) vs. 10 (2.3%); high-risk for preeclampsia in 1st trimester: 6 (3.4%) vs. 24 (5.6%); foetal anomaly in first trimester: 1 (0.6%) vs. 2 (0·5%); foetal anomaly in anatomy scan: 1 (0.6%) vs. 8 (1.9%); preterm delivery: 13 (7.5%) vs. 28 (6.5%); stillbirth: 2 (1.1%) vs. 0.0 (0); PROM: 31 (17.8%) vs. 44 (10.2%), *p = .011; PPROM: 5 (2.9%) vs. 5 (1.2%); PIH: 11 (6.4%) vs. 24 (5.8%); preeclampsia 7 (4%) vs. 23 (5.4%); obstetric haemorrhage: 6 (3.4%) vs. 20 (4.7%)	NICU admission: 12 (6.9%) vs. 7 (1.6%), *p = .001
20. Sourabh Verma	Outcomes of maternal-newborn dyads after maternal SARS-CoV-2	USA-New York	Cohort	149	Premature delivery: 16 (11%); GDM: 10 (7%); PIH: 17 (11%); foetal distress: 8 (5%); meconium-stained amniotic fluids: 23 (15%)	NICU admission: 18 (12%); neonatal demise: 1 (1%); respiratory distress: 13/148 (9%); RT-PCR positive for SARS-CoV-2: 1/87 (1%)
21. Najeh Hcini	Maternal, foetal and neonatal outcomes of large series of SARS-CoV-2 positive pregnancies in peripartum period: a single-centre prospective comparative study	France	Cohort	137+ vs. 370–	Preeclampsia/hypertension during pregnancy: 15 (10.9%) vs. 31 (8.3%); premature labour: 7 (5.1%) vs. 16 (4.3%); spontaneous preterm delivery <37 + 0 weeks: 11 (8.7%) vs.36 (10.0%); spontaneous preterm delivery <34 + 0 weeks: 1 (0.8%) vs. 9 (2.6%); GDM: 13 (9.4%) vs. 30 (8.1%); extremely preterm infants (22–23 + 6WG): 0 (0.0%) vs. 6 (1.6%); IUFD (19–35 W G): 7 (5.1%) vs. 4 (1.1%), *p = .0057; IUFD (19–35 W G): 7 (5.1%) vs. 4 (1.1%), *p = .0057; termination of pregnancy for foetal abnormalities: 3 (2.2%) vs. 1 (0.3%); meconium-stained amniotic fluid: 8 (6.3%) vs. 30 (8.4%); PPH: 18 (14.2%) vs. 26 (7.2%), *p = .0193	SGA foetus/foetal growth restriction: 3 (2.1%) vs.6 (1.6%); Apgar score ≤$7\mathrm{ }\text{at}\mathrm{ }1\mathrm{ }\min :\mathrm{ }14\mathrm{ }(11\mathrm{\%})\mathrm{ }\mathrm{vs}.31\mathrm{ }(8.5\mathrm{\%})\mathrm{ }0.5;\text{Apgar score }\le$ 7 at 5 min 4: (3.1%) 12 vs. (3.2%); RDS: 4 (3.1%) vs. 16 (4.3%); NICU admission: 3 (2.3%) vs. 12 (3.2%); SARS-CoV-2 RT PCR: 4/29 (13.8%)
22. Sara C Handley	Changes in preterm birth phenotypes and stillbirth at 2 Philadelphia hospitals during the SARS-CoV-2 pandemic, March–June 2020	USA	Cohort	3007 vs. 5907 prepandemic	Spontaneous preterm birth: 135 (4.7%) vs. 315 (5.7%); stillbirth: 15 (0.50%) vs. 32 (0.54%)
23. Amihai Rottenstreich	Vaginal delivery in SARS-CoV-2-infected pregnant women in Israel: a multicenter prospective analysis	Israel	Cohort	52	Preterm <37 weeks: 17 (32.7%), preterm <34 weeks: 9 (17.3%); GDM: 6 (11.5%); Gestational hypertensive disorders: 7 (13.4%); HELLP syndrome 1 (1.9%); PPH: 6 (11.5%)	5-min Apgar score < 8: 1 (1.9%); NICU admission: 6 (11.5%); RDS: 6 (11.5%); TTN: 1 (1.9%); hypoglycaemia: 4 (9.3%); hyperbilirubinemia: 5 (9.6%)
24. Ifeoma Ogamba	Initial review of pregnancy and neonatal outcomes of pregnant women with COVID-19 infection	USA	Cohort	40	Preterm 34–37 weeks: 1 (4%), <34 weeks: 3 (12%); PPH: 2 (8%); second trimester foetal loss: 2 (8%)	Preterm delivery, apnoea of prematurity: 1; hyperbilirubinemia: 1
25. Marjolein F Husen	Unique severe COVID-19 placental signature independent of severity of clinical maternal symptoms	Netherlands	Cohort	36	GDM: 6 (16.7%); hypertensive disorders: 2 (5.6%); spontaneous preterm delivery: 1 (2.8%); foetal distress: 7 (19.4%)	SGA: 9 (23.1%); Apgar <7 at 5 min: 5 (12.8%); pH <7.10: 2 (5.1%); neonatal SARS-CoV-2 positive: (1/39) 1 (2.6%)
26. Maryam Vizheh	Characteristics and outcomes of COVID-19 pneumonia in pregnancy compared with infected nonpregnant women	Iran	Cohort	110 pregnant and 234 nonpregnant	Spontaneous abortion: 8 (7.3%); GDM: 5 (4.5%); pre-eclampsia: 5 (4.5%); foetal distress: 9 (22.5%); preterm labour: 13 (11.8%); PROM: 5 (4.54%)	LBW: 12 (10.9%); NICU admission: 15 (29.4%); respiratory complications: 7 (13.7%); neonatal death: 2 (3.9%); neonatal positive SARS-CoV-2 result: 8 (15.7%)
27. Abdulrahman Al-Matary	Clinical outcomes of maternal and neonate with COVID-19 infection – multicenter study in Saudi Arabia	Saudi Arabia	Cohort	288	Premature or preterm delivery: 31 (15.5%); PROM: 16 (8%); fatal distress: 13 (6.5%); preeclampsia: 4 (2.0%); maternal mortality: 1 (0.5%); foetal death: 4 (2.0); IUGR: 3 (1.5%)	LBW: 29 (14.5%); birth weight >4000 g: 1 (0.5%); 1-min Apgar score <5: 18 (9.0%); 5-min Apgar score <5: 5 (2.5%); NICU admission: 86 (43.0%)
28. Itzíar Carrasco	SARS-COV-2 infection in pregnant women and newborns in a Spanish cohort (GESNEO-COVID) during the first wave	Spain	Cohort	105/107 newborns	Preterm birth: 21 (20.6%)	SGA: 6 (5.61%); NICU admission: 18 (16.8%); RT-PCR at 15 days positive 1 (0.93%)
29. Torri D Metz	Disease severity and perinatal outcomes of pregnant patients with coronavirus disease 2019 (COVID-19)	USA	Cohort	1219	Maternal mortality: 6; PPH: 108; hypertensive disorders of pregnancy: 285; abortion: 13; foetal death: 10; spontaneous preterm birth: 75	SGA: 126; NICU admission: 254; neonatal death: 5
30. Edward Mullins	Pregnancy and neonatal outcomes of COVID-19: coreporting of common outcomes from PAN-COVID and AAP-SONPM registries	UK	Cohort	651	Maternal mortality: 3 (0.5%); miscarriage: 12/647 (1.9%); Intrauterine death/stillbirth: 4/647 (0.6%); preterm delivery (live births only): 100/622 (16.1%); spontaneous onset of preterm labour and vaginal delivery (live births only): 22/621 (3.5%)	Early neonatal death: 2/614 (0.3%); positive neonatal SARS-CoV-2: 13/131 (9.9%)
31. Virginia Engels Calvo	Perinatal outcomes of pregnancies resulting from assisted reproduction technology in SARS-CoV-2-infected women: a prospective observational study	Spain	Cohort	1347	Preterm deliveries: 148; PROM: 209; PPROM: 37; haemorrhagic events: 71; abruptio placentae: 12; PPH: 61; DIC: 4; gestational hypertensive disorders: 69; moderate preeclampsia: 41; severe preeclampsia: 28; stillbirth: 10; maternal mortality: 2 (0.15%)	Apgar 5 score <7: 13; NICU admission: 137; neonatal mortality: 6 (0.44%)
32. Justine Chinn	Characteristics and outcomes of women with COVID-19 giving birth at US academic centres during the COVID-19 pandemic	USA/California	Cohort	18,715+ vs. 850,364–	Preterm birth: 3072 (16.4%) vs. 97 967 (11.5%), *p < .001; maternal mortality: 24 (0.1%) vs. 71 (<0.01%), *p <.001
33. José Villar	Maternal and neonatal morbidity and mortality among pregnant women with and without COVID-19 infection: the INTERCOVID Multinational Cohort Study.	18 countries^a	Cohort	706+ vs. 1424–	Vaginal bleeding; 44 (6.2%) vs. 87 (6.1%); PIH: 58 (8.2%) vs. 80 (5.6%); preeclampsia/eclampsia/HELLP: 59 (8.4%) vs. 63 (4.4%); preterm labour: 52 (7.4%) vs. 88 (6.2%); maternal mortality: 11 (1.6%) vs. 1 (0.1%); foetal distress: 87 (12.3%) vs. 120 (8.4%); PROM: 114 (16.1%) vs. 262 (18.4%); spontaneous preterm birth: 27 (3.8%) vs. 66 (4.6%)	LBW: 145 (20.5%) vs. 181 (12.7%); SGA: 97 (13.7%) vs. 181 (12.7%)
34. Erica M Lokken	Disease severity, pregnancy outcomes and maternal deaths among pregnant patients with severe acute respiratory syndrome coronavirus 2 infection in Washington State	USA	Cohort	240	Maternal mortality: 3 (1.3%); stillbirth: 2 (1.3%); preterm birth: 15 (9.7%); GDM: 16 (10.3%); new-onset hypertensive disorder of pregnancy or postpartum: 19 (12.3%)	LBW: 7 (4.6%); NICU admission: 11 (7.1%)
35. Ann-Christin Tallarek	Inefficient placental virus replication and absence of neonatal cell-specific immunity upon SARS-CoV-2 infection during pregnancy	Germany	Cohort	42	Preterm delivery: 10 (24%); <34 weeks: 2 (5%)	NICU admission: 7 (17%)
36. Daniel Katz	The Society for Obstetric Anaesthesia and Perinatology Coronavirus Disease 2019 Registry: an analysis of outcomes among pregnant women delivering during the initial severe acute respiratory syndrome coronavirus-2 outbreak in the United States.	USA	Cohort	490+ vs. 964–	GDM: 33 (6.7%) vs. 67 (7.0%); hypertensive disorders of pregnancy: 75 (15.3%) vs. 123 (12.8%); preterm delivery: 72 (14.8%) vs. 98 (10.2%), *p = .011; placental abruption: 6 (1.2%) vs. 10 (1.0%); PPH > 500 mL for vaginal delivery: 35 (11.4%) vs. 66 (10.5%); PPH >1 L for caesarean delivery: 18 (10.8%), 40 (12.2%)	Neonatal composite outcome: 97 (19.6%) vs. 164 (16.5)
37. Francesco D'Antonio	Maternal and perinatal outcomes in high compared to low risk pregnancies complicated by severe acute respiratory syndrome coronavirus 2 infection (phase 2): the World Association of Perinatal Medicine Working Group on Coronavirus Disease 2019	25 countries in Europe, the United States, South America, Asia and Australia	Cohort	887	Preterm birth at <37 weeks: 94; preterm birth at <34 weeks: 41; miscarriage: 22; IUFD: 5	Neonatal death: 8; perinatal death: 13; NICU admission: 72
38. Fulvia Milena Cribiù	Severe SARS-CoV-2 placenta infection can impact neonatal outcome in the absence of vertical transmission	Italy	Cohort	21+/16–	GDM: 2 (10%) vs. 3 (19%); gestational cholestasis: 1 (5%) vs. 0(0%); IUGR: 0 (0%) vs. 1(6%); AF anomalies 2 (10%) vs. 0(0%); PROM: 2 (10%) vs. 2 (12%); PPROM: 1 (5%) vs. 1 (6%); foetal complications: 2 (10%) vs. 0 (0%); foetal malformation: 1 (5%) vs. 0 (0%); therapeutic miscarriage: 1 (5%) vs. 0 (0%); macrosomia: 0 (0%) vs. 1 (6%); suspected chorioamnionitis: 0(0%) vs. 0 (0%); premature delivery: 6 (29%) vs. 3(19%); foetal distress: 2 (10%) vs.4 (25%)
39. Hilde Engjom	COVID-19 in pregnancy – characteristics and outcomes of pregnant women admitted to hospital because of SARS-CoV-2 infection in the Nordic countries	Nordic countries (Denmark, Finland, Iceland, Norway, Sweden)	Cohort	48/51 infant	Preterm delivery: 12/48 (25%)	NICU admission: 7/51 (13.7%)
40. Enrico Ferrazzi	Vaginal delivery in SARS-cov-2-infected pregnant women in Northern Italy: a retrospective analysis	Italy	Cohort	42	GDM: 6 (14%); preterm birth: 11 (spontaneous preterm: 5; elective caesarean section: 6)	NICU admission: 3; positivity to SARS-Cov-2: 3
41. Noelle Breslin	COVID-19 infection among asymptomatic and symptomatic pregnant women: two weeks of confirmed presentations to an affiliated pair of New York City hospitals	USA New York	Cohort	43	Preterm labour (n = 1); PIH: 1; foetal distress: 3	NICU admission: 3
42. Ming-zhu Yin	Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy in China: a retrospective cohort study	China	Cohort	31	Premature delivery: 5/17	LBW: 1/17
43. Marian Knight	Characteristics and outcomes of pregnant women admitted to hospital with confirmed SARS-CoV-2 infection in UK: national population based cohort study	United Kingdom	Cohort	427	GDM: 50 (12%); maternal mortality: 5 (1%); pregnancy loss: 4 (1%); stillbirth: 3 (1%); preterm: 70	Neonatal death: 2 (1%); NICU admission: 67/267 (live born infants only) (25%); positive SARS-CoV-2 test (liveborn infants only): 12/256 (4.6%)
44. Rafael San-Juan	Incidence and clinical profiles of COVID-19 pneumonia in pregnant women: a single-centre cohort study from Spain	Spain	Cohort	32/6 delivery	Preterm: 2/6	LBW: 2 RDS: 1; intraventricular haemorrhage grade 1: 1
45. AM Rebecca Pierce-Williams	Clinical course of severe and critical COVID-19 in hospitalised pregnancies: a US cohort study.	USA	Cohort	64	Hypertensive disorders of pregnancy: 2 (3%); magnesium sulphate for preeclampsia: 1 (2%); IUGR: 2 (3%); oligohydramnios: 1 (2%); presumed chorioamnionitis or endometritis: 3 (9%); PPH: 3 (9%); preterm delivery at <37 weeks: 19 (59%); preterm delivery at <34 weeks: 10 (31%); spontaneous preterm labour: 2 (6%); PPROM: 1 (3%)	NICU admission: 21 (63.6%)
46. Viktoriya London	The relationship between status at presentation and outcomes among pregnant women with COVID-19	USA	Cohort	68/55 of the 68 have delivered	GDM: 7 (10.3%); cholestasis of pregnancy: 2 (2.9%); preterm birth <37 weeks: 9 (16.4%); preterm birth <34 weeks: 3 (5.5%); PPH: 2 (3.6%); preeclampsia: 4 (7.3%)	–
47. Rasha Khoury	Characteristics and outcomes of 241 births to women with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at Five New York City Medical Centres.	USA	Cohort	241	Stillbirth: 2/247 (0.8%); singleton preterm birth (<37 weeks): 34/233 (14.6%); singleton early preterm birth (<34 weeks): 10/233 (4.3%); mal-presentation: 5/100 (5%)	Resuscitation at delivery: 70/233 (30.0%); NICU admission: 61/237 (25.7%); NRDS: 14/241 (5.8%); complications of prematurity or LBW: 21/241 (8.7%); sepsis: 1/241 (0.4%); congenital anomaly: 8/241 (3.3%); neonatal COVID-19 test result positive 6/236 (2.5%)
48. Valeria M Savasi	Clinical findings and disease severity in hospitalised pregnant women with coronavirus disease 2019 (COVID-19)	Italy	Cohort	77	Preterm delivery: 12 (21%)	NICU admission: 9 (16%); newborn COVID-19 test result, positive: 4 (7%)
49. Christine M Salvatore	Neonatal management and outcomes during the COVID-19 pandemic: an observation cohort study	USA	Cohort	116	Preterm (<37 weeks): 14; PROM: 96	LBW: 12 NICU admission: 12
50. Kate R Woodworth	Birth and infant outcomes following laboratory-confirmed SARS-CoV-2 infection in pregnancy – SET-NET, 16 jurisdictions, March 29–October 14, 2020	USA	Cohort	4442	PIH: 211 (7.6%); GDM: 228 (8.2%); pregnancy loss: 32 (0.7%); pregnancy loss <20 weeks: 12 (0.3%): pregnancy loss ≥20 weeks: 20 (0.4%): preterm (<37 weeks): 506 (12.9%); late preterm (34–36 weeks): 357 (9.1%); late preterm (34–36 weeks): 357 (9.1%); moderate preterm (32–33 weeks): 50 (1.3%); very preterm (28–31 weeks): 69 (1.8%); extremely preterm (<28 weeks): 30 (0.8%)	NICU admission among term live births: 279/2995 (9.3%); birth defects among live births: 28/4447 (0.6%)
51. Miranda J Delahoy	Characteristics and maternal and birth outcomes of hospitalised pregnant women with laboratory-confirmed COVID-19 – COVID-NET, 13 states, March 1–August 22, 2020	USA	Cohort	598	GDM: 64/581 (11.0%); hypertensive disorders of pregnancy: 70/581 (12.0%); IUGR: 11/581 (1.9%); pregnancy loss: 10/458 (2.2%); pregnancy loss at <20 weeks’ gestation: 4/458 (0.9%); pregnancy loss at ≥20 weeks’ gestation: 5/458 (1.1%); pregnancy loss at unknown gestational age 1/458 (0.2%); maternal mortality: 2/598 (0.3%)	Neonatal death: 2/448 (0.4%)
52. Claudio Fenizia	Analysis of SARS-CoV-2 vertical transmission during pregnancy	Italy	Cohort	31	Preterm delivery: 1 (3%)	NICU admission: 2 (6%); APGAR score 5′ <7: 1 (3%); infected neonates, positive: 2 (6%)
53. Dilek Sahin	Updated experience of a tertiary pandemic centre on 533 pregnant women with COVID‐19 infection: a prospective cohort study from Turkey.	Turkey	Cohort	533	Maternal mortality: 2 (0.4%); threatened abortion: 2 (0.3%); miscarriage: 12 (2.2%); hyperemesis gravidarum: 2 (0.3%); cholestasis of pregnancy: 5 (0.9%); foetal anomaly: 3 (0.5%); intrauterine foetal demise: 1 (0.2%); foetal growth restriction: 5 (0.9%); GDM: 3 (0.5%); PIH: 4 (0.7%); preterm delivery: 22 (4.1%); pre-eclampsia: 5 (0.9%); placental abruption: 1 (0.2%); deep vein thrombosis: 1 (0.2%); pregnancy loss: 13 (2.4%); foetal distress: 12 (13.8%)	Macrosomia 5 (5.7%); NICU admission: 13 (9.9%)
54. Jayasree Santhosh	Clinical characteristics of COVID‐19 in pregnant women: A retrospective descriptive single‐centre study from a tertiary hospital in Muscat, Oman	Oman	Cohort	60	Hypertension: 3 (5%); GDM: 15 (25%); preterm: 18 (30%); (late preterm delivery (34–36 + 6): 14 (24%); early preterm delivery (24–33 + 6): 4 (6.8%)); amniotic fluid, meconium stain (7/47): 7 (15%); PPROM: 1 (2.0%); preeclampsia: 4 (6.7%); preterm labour: 8 (16%); PPH: 2 (3.3%); pulmonary embolism: 2 (3.3%); pelvic haematoma: 1 (2.0%); miscarriage: 4 (6.7%); macerated stillbirth (47/60): 1 (2.1%)	LBW <2500 g (47/60) 15 (32%)
55. Mahtab Sattari	Evaluating clinical course and risk factors of infection and demographic characteristics of pregnant women with COVID-19 in Hamadan Province, West of Iran.	Iran	Cohort	50/26 have not given birth yet	Maternal mortality: 2 (4%); preterm delivery: 7 (29.2%)	Infection of the newborn according to Covid-19: 7 (28%)
56. Yan-Ting Wu	Neonatal outcome in 29 pregnant women with COVID-19: a retrospective study in Wuhan, China	China	Cohort	29/30 newborn	Gestational hypertensive disorder: 2 (6.90%); GDM: 3 (10.34%); gestational anaemia: 3 (10.34%); PPROM: 5 (17.24%); foetal distress: 3 (10.34%); preterm: 3 (10.34%)	COVID-19 diagnosis 2 confirmed and 3 suspected
57. Laura D Zambrano	Update: characteristics of symptomatic women of reproductive age with laboratory-confirmed SARS-CoV-2 infection by pregnancy status – United States, January 22–October 3, 2020	USA	Cohort	23,434	Maternal mortality: 34 (1.5%) (a total of 5152 (22.0%) pregnant women and 66,346 (17.2%) nonpregnant women were missing information on death and were assumed to have survived)
58. Malavika Prabhu	Pregnancy and postpartum outcomes in a universally tested population for SARS‐CoV‐2 in New York City: a prospective cohort study	USA	Cohort	70/73 newborn	Pre-eclampsia or PIH: 11; GDM: 6; preterm birth <37 weeks: 11; malpresentation: 1; Intrapartum fever: 7; PPH >1000 mL: 3; postpartum fever: 8	NICU admission: 13 (17.8%)
59. Amanda Dhuyvetter	Coronavirus disease 2019 in pregnancy: the experience at an urban safety net hospital	USA	Cohort	23	GDM: 1 (4.3%);PIH: 2 (8.7%); cholestasis of pregnancy: 2 (8.7%)	SGA: 1 (4.3%)
60. Mohsen AA Farghaly	Characteristics of newborns born to SARS-CoV-2-positive mothers: a retrospective cohort study	USA	Cohort	15	Preterm: 2 (13.3%)	NICU admission: 10 (66.7%); nursery admission: 5 (33.3%)
61. Mónica Ríos-Silva (Silva et al. 2020)	COVID-19 mortality among pregnant women in Mexico: a retrospective cohort study	Mexico	Cohort	448	Maternal mortality: 10 (2.2%)
62. Niyazi Tug	Pregnancy worsens the morbidity of COVID-19 and this effect becomes more prominent as pregnancy advances	Turkey	Cohort	188	Extremely preterm: 1/60 (1.7%), very preterm: 2/60 (3.3%), moderate/late preterm: 11/60 (18.3%); preeclampsia: 6 (3.2%); GDM: 1; placenta previa: 1
63. Rong Yang	Pregnant women with COVID-19 and risk of adverse birth outcomes and maternal–foetal vertical transmission: a population-based cohort study in Wuhan, China	China	Cohort	65	PIH: 3 (5%); preeclampsia: 1 (1%); GDM: 3 (5%); PROM: 4 (6%); preterm birth: 9 (14%)
64. Wei Liu	Clinical analysis of neonates born to mothers with or without COVID-19: a retrospective analysis of 48 cases from two neonatal intensive care units in Hubei Province	China	Cohort	15	Hypertensive disorders: 2 (13.3%); GDM: 2 (13.3%); chorioamnionitis: 2 (13.3%); PPH: 1 (6.7%)
65. Puneet Gupta	SARS-CoV-2 prevalence and maternal–perinatal outcomes among pregnant women admitted for delivery: experience from COVID-19-dedicated maternity hospital in Jammu, Jammu and Kashmir (India)	India	Cohort	108+ vs. 3057–	Preterm: 31 (28.3%) vs. (14.6%)*; maternal mortality: 1 (0.9%) vs. 7 (0.22%); GDM: 16 (14.8%) vs. 334 (10.9%); PIH: 12 (11.1%) vs. 264 (7.39%); intrahepatic cholestasis: 10 (9.2%) vs. 212 (6.93%); antepartum haemorrhage: 6 (5.55%) vs. 132 (4.3%); PPH: 5 (4.6%) vs. 110 (3.59%); foetal distress: 24 (22.2%) vs. 334 (10.9%), *p < .001	Birth weight, *p < .0001; NICU admission: 14 (12.9%) vs. 254 (8.3%); neonatal deaths: 2 (1.9%) vs. 42 (1.3)
66. Adhikari	Pregnancy outcomes among women with and without severe acute respiratory syndrome coronavirus 2 infection	USA	Cohort	252 SARS-CoV-2-positive and 3122 negatives	Abortion: 7 (3%) vs. 87 (3%); GDM: 14 (6%) vs. 207 (7%); severe preeclampsia: 26 (11%) vs. 359 (12%); abruption: 0 (0.0%) vs. 24 (1%); clinical chorioamnionitis: 24 (10%) vs. 345 (11%); stillbirth: 0 (0%) vs. 18 (0.6%); excessive blood loss (haemorrhage): 17 (7%) vs. 278 (9%); meconium-stained amniotic fluid: 53 (22%) vs. 571 (19%)	SGA: 31 (13%) vs. 316 (10%); 5-min Apgar score <4: 0 (0%) vs. 37 (1.2%); umbilical cord blood pH <7.0 d: 1 (0.4%) vs. 9 (0.3%); positive infants: 6
67. Milbak	A prospective cohort study of confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection during pregnancy evaluating SARS-CoV-2 antibodies in maternal and umbilical cord blood and SARS-CoV-2 in vaginal swabs	Denmark	Cohort	28 pregnant women with SARS‐CoV‐2 infection	PIH: 1 (3.6%); deep venous thrombosis: 1 (3.6%); pulmonary embolism: 1 (3.6%); GDM: 2 (7.1%); preterm delivery (<37 + 0 weeks): 2 (7.1%)	Apgar (5 min) <7: 1 (3.6%); NICU: 3 (10.7%); neonatal death: 1 (3.6%)
68. Ward	The clinical impact of maternal COVID-19 on mothers, their infants, and placentas with an analysis of vertical transfer of maternal SARS-CoV-2-specific IgG antibodies	USA	Cohort	115 mothers with SARS-CoV-2	PIH: 16 (13.9%); GDM: 11 (9.57%); meconium: 16 (13.9%); chorioamnionitis: 7 (6.09%); PPROM/PROM: 3 (2.61%); IUGR: 4 (3.48%); nuchal chord: 13 (11.3%); haemorrhage: 14 (12.2%); foetal intolerance: 14 (12.2%); failure to progress: 9 (7.83%); preeclampsia/HELLP syndrome: 15 (13.0%); preterm labour: 1 (0.87%); abruptio placenta: 1 (0.87%); retained placenta: 1 (0.87%); oligohydramnios: 1 (0.87%); shoulder dystocia: 1 (0.87%)	NICU/PICU admission: 23 (20.0%); premature (<37 weeks): 14 (12.2%); LGA: 8 (6.96%); SGA: 4 (3.48%); newborns tested for SARS-CoV-2 positive: 1 (1.47%)
69. Péju	Management and outcomes of pregnant women admitted to intensive care unit for severe pneumonia related to SARS-CoV-2 infection: the multicenter and international COVIDPREG study	France	Cohort	187 pregnant women with COVID-19	Abortion: 4; PIH: 10; GDM: 48; preeclampsia: 8; mortality: 2; PPH: 11; stillbirth: 3; preterm birth (<32 weeks’ gestation): 47; preterm birth (<37 weeks’ gestation): 79	Foetal or neonatal mortality: 8; SGA: 9
70. Seyed- Abdolvahab Taghavi	Obstetric, maternal and neonatal outcomes in COVID-19 compared to healthy pregnant women in Iran: a retrospective, case-control study	Iran	Case-control	Case = 55/control = 55	GDM: 4 (7.27) vs. 2 (3.63); PIH: 2 (3.63) vs. 1 (1.81); abortion <21 weeks: 3/14 (21.42) vs. 2/14 (14.28); IUFD: 0 vs. 1/20 (5); PPH: 1/20 (5) vs. 3/20 (15); preterm birth: 5/20 (25) vs. 2/20 (10), *p value <.05; foetal distress: 2/20 (10) vs. 1/20 (5)	LBW: 2/20 (10) vs. 1/20 (5); Apgar in 5 min <7: 3/20 (15) vs.4/20 (20); respiratory distress: 3/20 (15) vs. 1/20 (5); NICU admission: 2/20 (10) vs. 3/20 (15), neonatal dead: 1/20 (5) vs. 0
71. Justin S. Brandt	Epidemiology of coronavirus disease 2019 in pregnancy: risk factors and associations with adverse maternal and neonatal outcomes	USA	Case-control	61 cases/122 controls	Preterm delivery: <37 weeks: 7 (11.5%) vs.10 (8.2%); <34 weeks: 4 (6.6%) vs. 4 (3.3%); <28 weeks: 2 (3.3%) vs. 1 (0.8%); chorioamnionitis: 2 (3.3%) vs. 2 (1.6%); preeclampsia: 6 (9.8%) vs. 10 (8.2%)	NICU admission: 53 (86.9%) vs. 14 (11.5%); RDS: 5 (8.2%) vs. 6 (4.9%); intraventricular haemorrhage: 2 (3.3%) vs. 1 (0.8%); neonatal death: 1 (1.6%) vs. 1 (0.8)
72. MP Tadas	Maternal and neonatal outcomes of pregnant women with covid-19: a case-control study at a tertiary care centre in India	India	Case-control	181 vs. 181	Pregnancy morbidity: 100 (55.24%) vs. 54, *p = .000; stillbirth: 7 vs. 7	NICU admission: 14 vs. 16; neonatal death: 1 vs. 3
73. Na Li	Maternal and neonatal outcomes of pregnant women with COVID-19 pneumonia: a case-control study	China	Case-control	Confirmed (n = 16); suspected (n = 18)/control 2020 (n = 121) Control 2019 (n = 121)	Preeclampsia: 1; PIH: 3; GDM: 3; hypothyroidism: 2; PROM: 1; placental abruption: 1 in 16 confirmed cases; preterm delivery: 3 (18.8%), 3 (16.7%) vs. 7 (5.8%), 6 (5.0%); intrauterine foetal distress: 2 (11.7%), 1 (5.3%) vs.6 (5.0%) and 6 (5.0%) in confirmed case, suspected case vs. control 2020 and 2019, respectively	Premature birth: 4 (23.5%), 4 (21.1%) 7 vs. (5.8%) and 6 (5.0%); low birth weight: 3 (17.6%), 2 (10.5%) vs. 3 (2.5%) and 3 (2.5%) in confirmed case, suspected case vs. control 2020 and 2019, respectively
74. Guoqiang Sun	Blood test results of pregnant COVID-19 patients: an updated case-control study	China	Case-control	60	Preterm: 10 (16.67)

GDM: gestational diabetes mellitus; PIH: pregnancy-induced hypertension (gestational hypertension); PP/PA: placenta previa/accrete; IUGR: intrauterine growth restriction; AF: amniotic fluid; PROM: premature rupture of membrane; PPROM: preterm premature rupture of membrane; PPH: postpartum haemorrhage; NRDS: neonatal respiratory distress syndrome; GTT: glucose tolerance test; HELLP: haemolysis elevated liver enzymes, and low platelets; RDS: respiratory distress syndrome; TTN: transient tachypnoea of the newborn; HELLP: haemolysis elevated liver enzymes, and low platelets; DIC: disseminated intravascular coagulation.

*Statistically significant differences p < .05.

^aArgentina, Brazil, Egypt, France, Ghana, India, Indonesia, Italy, Japan, Mexico, Nigeria, North Macedonia, Pakistan, Russia, Spain, Switzerland, UK and the US.

The articles were published in various geographical regions. Most studies were conducted in China (45 studies) or the United States (34 studies). Ten studies compared the pregnancy outcomes before and during the COVID-19 pandemic or lockdown (Ashish et al. 2020, Justman et al. 2020, Cauldwell et al. 2021, Du et al. 2021, Goyal et al. 2021, Kirchengast and Hartmann 2021, Ranjbar et al. 2021, Rotshenker-Olshinka et al. 2021, Shakespeare et al. 2021, Wilk et al. 2021). Tables S3–S6 show the summary of the main characteristics of the studies included in the systematic review.

Meta-analysis of outcomes

Figures S1–S11 illustrate the forest plots of the pooled prevalence of pregnancy outcomes in pregnant women with and without Covid infection. Results showed that the pooled prevalence of preterm delivery, maternal mortality, NICU admission and neonatal death in the group with COVID-19 infection (14.32 (95% CI: 12.07, 16.91), 0.65 (95% CI: 90.37, 1.130), 14.57 (95% CI: 10.15, 20.48), 0.65 (95% CI: 0.51, 0.83), respectively) were significantly more than those without COVID-19 infection (5.57 (95% CI: 3.2, 9.52), 0.02 (95% CI: 0.01, 0.11), 4.53 (95% CI: 2.45, 8.22), 0.06 (95% CI: 0.05, 0.08), respectively).

There was no significant difference in the pooled prevalence of other pregnancy outcomes including PROM, GDM, hypertensive disorders, IUGR/SGS, LBW, PPH and pregnancy loss. The pooled prevalence of SARS-CoV2 positive neonates was 2.04 (95% CI: 1.71; 2.45).

The meta-regression results showed that the mean prevalence of pregnancy loss in lower middle income and upper middle-income countries were 1.23% (p value = .03) and 1.27% (p value = .001) higher than in high-income countries, respectively. The mean prevalence of SARS-CoV2 positive neonates in lower middle income was 1.04% higher than in high-income countries (p value = .009). While the mean prevalence of PPH in lower middle-income countries was 1.3% lower than high-income countries (p value = .016). Table 2 shows results of the meta-regression using income level of countries (according to the World Bank classification).

Table 2. Results of the meta-regression using income level of countries (according to the World Bank classification).

Outcome	High income (reference)	Lower middle income		Upper middle income
	Coefficient	Coefficient (95% CI)	p Value	Coefficient (95% CI)	p Value
GDM	1	–0.63 (–1.59, 0.32)	.195	–0.26 (–0.73, 0.21)	.258
Hypertensive disorders	1	–0.91 (–2.45, 0.63)	.248	–0.31 (–0.74, 0.12)	.163
IUGR/SGA^a	1	–	–	–1.42 (–3.26, 0.41)	.129
LBW	1	–0.30 (–1.38, 0.78)	.583	0.08 (–1.01, 1.17)	.891
Maternal mortality	1	1.82 (–0.82, 4.45)	.176	1.59 (–0.03, 3.21)	.054
Neonatal death	1	1.30 (–0.42, 3.02)	.138	1.25 (–0.49, 2.99)	.160
NICU admission	1	–0.36 (–1.57, 0.84)	.553	–0.08 (–1.09, 0.93)	.875
PPH	1	–1.30 (–2.35, −0.24)	.016	–0.67 (–1.49, 0.15)	.109
Pregnancy loss	1	1.23 (0.48, 1.98)	.001	1.27 (0.11, 2.41)	.030
Preterm delivery	1	0.01 (–0.88, 0.91)	.974	–0.02 (–0.55, 0.51)	.93
PROM	1	–0.29 (–1.98, 1.40)	.736	–0.44 (–1.44, 0.55)	.384
SARS-CoV2 positive neonates	1	1.04 (0.26, 1.81)	.009	0.30 (–0.58, 1.19)	.504

^aThere was no sample for the lower middle-income countries.

Publication bias

Figures S12–S23 show the funnel plots of the results of publication biases based on Egger’s test in adverse pregnancy outcomes.

Egger’s test shows significant publication biases among studies investigating the prevalence of hypertensive disorders (p value = .02), LBW (p value=.03), maternal mortality (p value < .001) and pregnancy loss (p value < .001) which were adjusted by the trim and fill method. Figures S24–S27 show the results of the trim and fill of these pregnancy outcomes.

Quality assessment

Quality assessment based on the Critical Appraisal Checklist showed that among seven case-control studies, four studies were classified as being of high quality (8–10 score) and three studies had moderate quality (5–7 score); among 28 case series, 18 studies were classified as being of high quality (7–8 score) and 10 studies had moderate quality (5–6 score); among of 26 cross-sectional, two studies were classified as being of high quality (7–8 score), 22 studies had moderate quality (5–6 score) and two studies had low quality (≤4 scores); among 80 cohort studies, 67 studies were classified as being of high quality (9–11 score) and 13 studies had moderate quality (6–8 score). As shown in Table S2, among the total of 141 studies, 71.5% had high quality, 44.2% medium and the rest (two articles) had low quality.

Feto-maternal outcomes

Comparison of outcomes in patients with or without COVID-19 in included analytical studies showed a significant difference in the outcomes of preterm birth (Marín Gabriel et al. 2020, Abedzadeh‐Kalahroudi et al. 2021, Chinn et al. 2021, Cruz Melguizo et al. 2021, Gupta et al. 2021, Katz et al. 2021, Milln et al. 2021, Taghavi et al. 2021, Timircan et al. 2021), PROM (Cruz-Lemini et al. 2021, Cruz Melguizo et al. 2021, Du et al. 2021, Timircan et al. 2021), PPROM (Cruz Melguizo et al. 2021), prematurity, GDM (Ko et al. 2021), gestational hypertension (Ko et al. 2021), pre-eclampsia/eclampsia (severe pre-eclampsia and moderate pre-eclampsia) (Abedzadeh‐Kalahroudi et al. 2021, Cruz Melguizo et al. 2021, Ko et al. 2021, Wilk et al. 2021), foetal distress (Abedzadeh‐Kalahroudi et al. 2021, Gupta et al. 2021), stillbirth (Cruz Melguizo et al. 2021), pregnancy morbidity (Tadas et al. 2021), IUFD (Hcini et al. 2021), PPH (Hcini et al. 2021), maternal mortality (Chinn et al. 2021), and prolonged labour (Wilk et al. 2021). Maternal mortality has been reported in 26 studies, but only in one analytical study there was a significant difference between patients with and without COVID-19 infection (Chinn et al. 2021).

Some studies have compared the pregnancy outcomes before and during the COVID-19 pandemic. The results of these studies have also been different. Some studies showed a significant difference in pregnancy outcomes such as high-risk pregnancies (Goyal et al. 2021), GDM, PROM (Du et al. 2021), hypertensive disorders/pre-eclampsia (Justman et al. 2020, Wilk et al. 2021), stillbirth (Ashish et al. 2020), prolonged labour (Wilk et al. 2021), between two periods, while other studies reported no significant change in maternal mortality or severe maternal morbidity (such as PPH, uterine rupture and severe preeclampsia/eclampsia) and stillbirth (Shakespeare et al. 2021).

Neonatal outcomes

Comparison of outcomes in patients with or without COVID-19 in included analytical studies showed a significant difference in the outcomes of prematurity (Timircan et al. 2021), NICU admission (Cruz-Lemini et al. 2021, Cruz Melguizo et al. 2021), neonatal admission (Milln et al. 2021) and birth weight (Gupta et al. 2021).

The comparison of neonatal outcomes in the two periods (before and during the COVID-19 pandemic) was not the same. Some studies have reported an increase in neonatal mortality (Du et al. 2021, Wilk et al. 2021), while some studies showed no significant change in NICU admissions or other outcomes (Justman et al. 2020, Du et al. 2021, Shakespeare et al. 2021, Wilk et al. 2021, Wagner et al. 2022).

Discussion

Since the onset of the COVID-19 epidemic in early 2020, there has been concern that the disease in pregnant women may have adverse effects on pregnancy outcomes. In this systematic review and meta-analysis, we summarise the result of 141 studies. The clinical characteristics, radiological and laboratory manifestations are similar in pregnant women with COVID-19 infection when compared with non-pregnant women or the general population. The result of a meta-analysis of 74 cohort and case-control studies showed that preterm delivery, maternal mortality, NICU admission and neonatal death in pregnant women with COVID-19 infection were significantly more than in those without COVID-19 infection.

This result is similar to the results of some meta-analyses performed. Karaçam et al. (2022) based on the results of a meta-analysis of 54 studies, reported that morbidity, preterm and caesarean birth rates necessitating admission to the intensive care unit as well as maternal and perinatal death rates were higher in pregnant women with COVID-19 and their infants (Karaçam et al. 2022). As Jafari et al. (2021) showed that preterm birth, caesarean delivery and LBW were more probable in women with COVID-19 compared to women without COVID-19 (Jafari et al. 2021). Gao et al. (2020) also reported that the rate of preterm labour in healthy pregnant women worldwide is lower than that in pregnant women with COVID-19. They believe that the probable reason for this higher rate is the higher rate of induction in women with COVID-19 in the third trimester of pregnancy. Most of these women also choose to give birth prematurely by caesarean section to prevent prolonged labour (Gao et al. 2020).

Our study showed that pregnancy loss and SARS-CoV2 positive neonates in lower middle income were higher than in high income. Consistent with this result, a meta-analysis by Yang et al. (2022) comparing pandemic and pre-pandemic periods showed that stillbirths were higher for middle-income countries but not for high-income countries (Yang et al. 2022).

The current systematic review showed that the most common signs and symptoms of pregnant women were fever, dry cough and fatigue. However, other less common symptoms, including headache, myalgia, nasal congestion, sore throat, dyspnoea, chills, body aches, conjunctivitis, skin rash, diarrhoea, loss of taste or smell, and discolouration of fingers or toes, have been reported (Hassanipour et al. 2020, Khan et al. 2020, Berghella and Hughes 2021, Saadaoui et al. 2021). In pregnant women, as in other adults, fever was a common clinical manifestation at the onset of COVID-19. Evidence has shown that intrapartum fever may lead to adverse neonatal outcomes (Dior et al. 2016). Jafari et al. (2021) based on a meta-analysis reported that pregnant women with COVID-19 had similar clinical, laboratory and imaging characteristics to non-pregnant adult patients in the general population (Jafari et al. 2021). A systematic review and meta-analysis found that being symptomatically varied across ethnicities, with black and Asian pregnant women more likely to be symptomatic, while white pregnant women were more likely to be asymptomatic (Khan et al. 2021).

Pregnant women are more susceptible to respiratory pathogens and pneumonia due to the immunosuppressive state as well as physiological differences which often lead to severe hypoxia (O'Day 1997, Ramsey and Ramin 2001, Mosby et al. 2011, Mertz et al. 2013, Chen et al. 2020, Liu et al. 2020a, 2020c). Therefore, infection with the COVID-19 during pregnancy is expected to increase the risk of maternal and foetal complications, and women with severe pneumonia to be more at risk for adverse pregnancy outcomes. But the results of different studies about the adverse pregnancy outcomes in women infected with COVID-19 were very different.

The comparison of the outcomes in patients with or without COVID-19 in analytical studies showed that some of the feto-maternal outcomes such as preterm birth (Marín Gabriel et al. 2020, Abedzadeh‐Kalahroudi et al. 2021, Chinn et al. 2021, Cruz Melguizo et al. 2021, Gupta et al. 2021, Katz et al. 2021, Milln et al. 2021, Taghavi et al. 2021, Timircan et al. 2021), PROM (Cruz-Lemini et al. 2021, Cruz Melguizo et al. 2021, Du et al. 2021, Timircan et al. 2021), PPROM (Cruz Melguizo et al. 2021), GDM (Ko et al. 2021), gestational hypertension (Ko et al. 2021), pre-eclampsia/eclampsia (Abedzadeh‐Kalahroudi et al. 2021, Cruz Melguizo et al. 2021, Ko et al. 2021, Wilk et al. 2021), foetal distress (Abedzadeh‐Kalahroudi et al. 2021, Gupta et al. 2021), stillbirth (Cruz Melguizo et al. 2021), pregnancy morbidity (Tadas et al. 2021), IUFD (Hcini et al. 2021), PPH (Hcini et al. 2021), maternal mortality (Chinn et al. 2021), and prolonged labour (Wilk et al. 2021) in pregnant women with Covid-19 were significantly more than in those without Covid.

The function of the immune system in pregnant women is very complex. Therefore, maternal and neonatal outcomes will be different in each pregnant woman based on gestational age, immune system, duration of infection, and severity of infection (Banaei et al. 2020).

There are different opinions about changes in the immune response in pregnant women. Some have suggested that the transition to a Th2 anti-inflammatory environment during pregnancy may result in protection from a severe COVID-19 presentation (Dashraath et al. 2020, Saadaoui et al. 2021). It has also been reported that COVID-19 infection during pregnancy was characterised by placental inflammation and reduced antiviral antibody responses, which may impact the efficacy of COVID-19 therapeutics in pregnancy (Sherer et al. 2020). In our systematic review, maternal mortality was uncommon. This result is consistent with the results of other review studies (Allotey et al. 2020, Khalil et al. 2020, Lassi et al. 2021, Saadaoui et al. 2021).

COVID-19 may be associated with some neonatal outcomes. Based on the comparison of the outcomes in patients with or without COVID-19 in analytical studies, the main adverse neonatal outcome found is iatrogenic preterm birth (Timircan et al. 2021), and neonatal or NICU admission (Cruz-Lemini et al. 2021, Cruz Melguizo et al. 2021, Milln et al. 2021). There is no evidence for congenital malformations associated with maternal infection.

Some studies showed that women with pneumonia during pregnancy were more likely to have preterm deliveries, LBW and SGA infants than women without pneumonia (Bánhidy et al. 2008, Brito and Niederman 2011, Romanyuk et al. 2011, Chen et al. 2012). Some studies have also reported that SARS during pregnancy is associated with high incidences of spontaneous miscarriage, preterm delivery and intrauterine growth restriction (Wong et al. 2004).

This finding is consistent with other review studies that reported that preterm delivery, foetal distress and LBW were the common pregnancy outcomes of women with COVID-19 (Banaei et al. 2020, Mullins et al. 2020, Mark et al. 2021).

A systematic review and meta-analysis to evaluate differences in pregnancy and perinatal outcomes among symptoms compared with asymptomatic pregnant women infected with COVID-19 showed that the mean birth weight was significantly lower, while the probability of LBW and preterm delivery was more common among symptomatic pregnant women (Khan et al. 2021). Another systematic study reported that preterm delivery before 37 weeks of gestation was common in 21.8% of pregnant women with COVID-19 (Khalil et al. 2020).

The possibility of vertical transmission of COVID-19 is a tremendous concern for both patients and neonatologists and neonatal health care providers. Information on vertical transmission of COVID-19 is limited in studies and there is controversial information about the vertical transmission of COVID-19. In our systematic review, 32 studies reported the number of positive newborns for COVID-19, which may indicate vertical transmission from mother to foetus or due to infection after birth and it is not clear whether the source of the reported infection in these neonates is from the mother or from the environment. Our meta-analysis showed that there were SARS-CoV2 positive in 2% of infected mothers neonates.

Wang et al. (2020) summarised that there is currently no evidence of intrauterine infection due to vertical transmission in women with COVID-19 in the third trimester of pregnancy, but it is unclear whether COVID-19 infection in the first or second trimester of pregnancy can carry the risk of vertical transmission or not? (Wang et al. 2020). Musa et al. (2021) based on a review of 69 studies, reported that most of the mother-to-child infection was likely due to environmental exposure, although a significant proportion was attributable to potential vertical transmission of SARS-CoV-2 (Musa et al. 2021).

However, in the majority of studies, there was no evidence of vertical transmission and the findings of some systematic reviews do not also support the possibility of vertical transmission of COVID-19 infection (Banaei et al. 2020, Islam et al. 2020, Mullins et al. 2020). The results of some meta-analyses also showed that the possibility of vertical transmission from mother to foetus is low (Jafari et al. 2021, Kotlyar et al. 2021). Current evidence suggests that neonates and children do not develop severe COVID-19, and neonatal mortality is rare. However, we must be careful about the possibility of vertical transmission. It is important to diagnose neonatal infection because neonates can play a role in creating community-related infections (Saadaoui et al. 2021).

The current systematic review and meta-analysis have several strengths. First, we included in this systematic review 141 studies and conducted a meta-analysis of 74 studies with a large number of pregnant women that contribute to a more comprehensive understanding of COVID-19 in pregnancy. Second, we followed the correct methodology for conducting the present systematic review. Third, this study presents pregnancy outcomes of COVID-19 from different countries’ perspectives. The limitation of this study was the high heterogeneity in methods, study designs and estimates, which made meta-analysis difficult for all of them, so we performed a meta-analysis on cohort and case-control studies. Another limitation is that we were only able to search for articles in the PubMed and Scopus databases, and it was not possible for us to access other databases. Also, we only included English language articles in the study.

The findings of this study, as well as recently published systematic reviews and meta-analysis, may help physicians understand the nature of the disease and make appropriate decisions when treating pregnant women with COVID-19. Certainly, early identification and intervention of patients can reduce adverse pregnancy outcomes and improve the consequences of pregnancy. However, further studies are needed to confirm the long-term outcomes and potential vertical transmission from mother to foetus. On the other hand, with the identification of new strains of COVID-19, there are still questions as to whether each of these strains has more severe effects on the mother, foetus and newborn.

Conclusions

COVID-19 infection during pregnancy may cause adverse pregnancy outcomes including preterm delivery, maternal mortality, NICU admission and neonatal death. Pregnancy loss and SARS-CoV2 positive neonates in lower middle income are higher than in high income. The findings and knowledge gained from our systematic review show that the reported pregnancy outcomes for women with COVID-19 were been varied. Although studies reported some feto-maternal and neonatal outcomes, future studies are needed to elucidate the causal relationship between these outcomes and COVID-19 infection. Vertical transmission from mother to foetus may occur, but its immediate and long-term effects on the newborn are unclear. Therefore, due to the high transmission capacity of this virus, the treatment team should be aware of the possibility of vertical transmission and take the necessary measures and attention. Also, if the mother is seriously ill, separation from the newborn should be considered.

Acknowledgements

The authors thank all authors of the primary studies included in this review.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information. The datasets generated during and/or analysed during the current study are available from the corresponding author upon reasonable request.