https://orcid.org/0000-0002-8484-0976
Abstract
Introduction
Effect of physical activity in pregnancy on preeclampsia (PE) and angiogenic markers is not well understood. We studied the association of physical activity and PE in a case-control setting and assessed whether exercise in PE and non-PE women associate with maternal serum concentrations of soluble fms-like tyrosine kinase 1 (s-Flt-1), placental growth factor (PlGF) and soluble endoglin (sEng) and sFlt-1/PlGF ratio in the Finnish Genetics of Pre-eclampsia Consortium (FINNPEC) cohort.
Materials and methods
Participants completed a questionnaire on their background information and serum samples were collected from a subset. Questionnaire data on physical activity were available from 708 PE women and 724 non-PE women. Both first trimester serum samples and questionnaire data on physical activity were available from 160 PE women and 160 non-PE women, and second/third trimester serum samples and questionnaire data on physical activity were available from 139 PE women and 47 non-PE women. The PE and non-PE women were divided into categories of physically active (exercise 2 − 3 times/week or more) and physically inactive (exercise less than 2 − 3 times/week).
Results
A total of 43.4% of the PE women and 42.4% of the non-PE women were categorized as physically active. There were no differences in physical activity and exercise habits between the groups. The physically active women were more often nulliparous and non-smokers and had a lower body mass index. There were no differences in the concentrations of angiogenic markers (sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio) between the groups who exercised more or less than 2 − 3 times/week.
Conclusions
In the FINNPEC study cohort, there was no association between physical activity and PE and no associations of physical activity in pregnant women with and without PE with maternal serum concentrations of sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio.
KEY MESSAGES
This is the first study to investigate the association of physical activity in pregnancy with concentrations of angiogenic markers while comparing pregnant women with and without preeclampsia.
There were no differences in the physical activity and exercise habits in pregnancy between women with and without preeclampsia in the FINNPEC cohort.
Physical activity of pregnant women with or without preeclampsia did not associate with the concentrations of angiogenic markers (sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio).
1. Introduction
Preeclampsia (PE) is a complex pregnancy-specific disorder that is characterized by new-onset hypertension and proteinuria after 20 weeks of gestation or new-onset signs of other maternal end-organ dysfunction or uteroplacental dysfunction in the absence of proteinuria [Citation1]. PE affects 3–5% of pregnancies and is one of the main causes of maternal, fetal and neonatal morbidity and mortality [Citation2]. The etiology of PE is largely unknown, and its prevention remains a challenge. Reduced placental perfusion and inflammation associated with oxidative stress and endothelial dysfunction are considered as central features in the pathogenesis of PE [Citation3].
Exercise during pregnancy has been suggested as protection from PE [Citation4–7], but the data are conflicting [Citation8–10]. The 2021 International Society for the Study of Hypertension in Pregnancy stated that exercise in pregnancy is recommended for all women without contraindications for a reduction of the likelihood of PE [Citation1]. To achieve these reductions, women should undertake at least 140 min per week of moderate-intensity exercise [Citation1]. The mechanisms by which exercise reduces the risk of PE are not well understood, but it has been suggested that exercise training promotes placental growth and vascular development, reduces oxidative stress and improves endothelial function as well as immune and inflammatory responses [Citation11].
Angiogenic markers are involved in the pathogenesis of PE [Citation12]. Circulating maternal serum levels of soluble fms-like tyrosine kinase 1 (s-Flt-1) and soluble endoglin (sEng) and sFlt-1/PlGF ratio are increased and levels of placental growth factor (PIGF) are decreased in PE as well as in pregnant women weeks prior to established PE [Citation13, Citation14].
There are limited data on angiogenic markers and exercise in pregnancy. In one small study, regular exercise during pregnancy was associated with higher serum PlGF and lower sFlt-1 and sEng concentrations in late non-complicated pregnancy [Citation15]. This kind of pro-angiogenic serum profile is hypothesized to contribute to the reduced risk of PE among physically active women [Citation15]. Exercise training during pregnancy was shown to decrease s-Flt-1 levels in a rat model of hypertension during PE [Citation16] and a rat model of PE superimposed on chronic hypertension [Citation17]. Human studies on the association of exercise in pregnancy, PE and angiogenic markers are lacking.
Our aims were first to study the association between physical activity and PE in a case-control setting and second to assess whether exercise in pregnant women with and without PE associate with maternal serum concentrations of sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio in the Finnish Genetics of Pre-eclampsia Consortium (FINNPEC) cohort.
2. Material and methods
2.1. Study design
The data consisted of the prospective arm of the FINNPEC cohort. FINNPEC, a cross-sectional case-control multicenter study, was established to set up a nationwide clinical and DNA database of pregnant women with and without PE, their partners and infants. The cohort was established in order to identify genetic risk factors for PE. The details of the study design, methods and procedures have been previously published [Citation18–20].
2.2. Study subjects
A total of 923 pregnant women with PE and 1009 controls (non-PE) were recruited for the study from 2008 to 2011. The inclusion criteria were age above 18 years, a singleton pregnancy and the ability to provide informed consent based on information in Finnish or Swedish. PE was defined as hypertension and proteinuria occurring after 20 weeks of gestation as based on the American College of Obstetricians and Gynecologists 2002 criteria [Citation21]. Hypertension was defined as systolic blood pressure ≥ 140 mmHg and/or diastolic blood pressure ≥ 90 mmHg. Proteinuria was defined as the urinary excretion of ≥ 0.3 g protein in a 24-h specimen, 0.3 g/l or two ≥ 1+ readings on a dipstick in a random urine sample with no evidence of a urinary tract infection. Each diagnosis was independently verified from medical records by a research nurse and research physician. The control group consisted of healthy women with uncomplicated pregnancies and women with pregnancy complications excluding PE, such as gestational diabetes, gestational hypertension, proteinuria without high blood pressure, placental insufficiency, PE in a previous pregnancy, fetal death and small for gestational age fetuses.
All participants provided written informed consent, and the FINNPEC study protocol was approved by the coordinating Ethics Committee of the Hospital District of Helsinki and Uusimaa (149/EO/2007).
The participants completed a detailed questionnaire on their background information that included data on physical activity during pregnancy. Information on age, pre-pregnancy weight and height, obstetric history, medical history, pregnancy complications, pregnancy outcome, blood pressure, delivery and newborn were obtained from hospital records and maternity cards. Data on smoking were collected from maternity cards and complemented by the background information questionnaires.
The questionnaire included eight questions about physical activity and exercise habits during pregnancy. The questions defined how much time was spent exercising, how strenuous the exercise was and if it was performed during work or leisure time. By combining the answers to different questions, two variables were set to divide the women into two categories according to their physical activity: physically active and inactive. A new variable (How often do you exercise?) was created from the question ‘How often do you exercise?’ with answer options: never, less than once a month, about once a week, 2–3 times a week, 4–5 times a week or approximately every day. The new variable divided women into categories of physically active (exercise 2 − 3 times/week or more) and physically inactive (exercise less than 2 − 3 times/week). We also created another variable (Do you exercise ≥ 2–3 times/week, ≥ 30 min at a time with at least moderate intensity? [Yes/No]) by combining data from three questions (How often do you exercise? How long does an average free-time exercise session last? Is your free-time exercise about as strenuous as alternating between walking and light running?). These categorizations were based on the recommendations of the Finnish Current Care Guidelines for exercise during pregnancy (exercise training at least 150 min/week divided among at least 3 days/week) [Citation22].
2.3. Serum samples and angiogenic markers
First and second/third trimester serum samples were available from women who received care in the Hospital District of Helsinki and Uusimaa. First trimester serum samples were obtained from the first trimester biochemical screening for fetal chromosomal abnormalities (range 9–15 weeks of gestation), and serum samples from the second/third trimesters (range 20–42 weeks of gestation) were collected at hospitals according to the study protocol.
Maternal serum sFlt-1 and PlGF concentrations were measured using sFlt-1 and PlGF electro-chemiluminescence immunoassays (ECLIA; Roche Diagnostics GmbH, Mannheim, Germany) on a cobas e 601 analyzer (Hitachi High Technology Co, Tokyo, Japan). Serum concentration of endoglin (CD105) was measured using a human Quantikine Endoglin ELISA kit (R&D Systems, UK) according to the manufacturer’s instructions.
2.4. Statistical analysis
Statistical tests were performed using SPSS Statistics 25.0 (IBM Corp., Armonk, NY, USA). The physical activity of the PE and non-PE women was compared. The maternal and perinatal characteristics of the PE and non-PE women were compared according to physical activity separately.
The normality of the variable distributions was verified graphically and with a Kolmogorov–Smirnov-test. The statistical analyses of the continuous variables were performed using two-sample t-tests for the normal distributions and Mann–Whitney U-tests for the skewed distributions. The categorical variable comparisons between the groups were performed with Chi-square tests. P values of < 0.05 were considered as statistically significant.
The first and second/third trimester serum concentrations of angiogenic markers in PE and non-PE women divided according to physical activity were compared. Logarithmic transformation was used when appropriate. Each biomarker was ln-transformed to correct for right-skewness, and estimated means were back-transformed as mean estimates/model-based means and 95% confidence intervals for purposes of presentation. Comparisons between groups were analyzed with a two-way analysis of variance (ANOVA). Selected co-variables (parity, maternal age, smoking status, body mass index [BMI]) were included in the models as covariates. The normality of the variable distributions was verified graphically and with a Kolmogorov–Smirnov-test.
3. Results
3.1. Physical activity
Information on the study participants’ physical activity is shown in . Questionnaire data on physical activity were available from 708 PE women and 724 non-PE women. A total of 43.4% of PE women and 42.4% of non-PE women exercised ≥ 2–3 times/week, ≥ 30 min at a time with at least moderate intensity and were thus categorized as physically active. The women with PE estimated their physical fitness to be poorer than did the non-PE women; however, there were no clear differences in physical activity and exercise habits between the groups. The women with PE spent less time daily doing household work, yard work and/or gardening than the non-PE women.
Table 1. Physical activity of the FINNPEC women.
3.2. Maternal and perinatal characteristics according to physical activity
The maternal and perinatal characteristics of the PE and non-PE women according to physical activity are presented in . Among both the PE and non-PE women, those who were physically active were more often nulliparous, non-smokers before and during pregnancy and had a lower BMI. In the non-PE group, the physically active women were younger and had fewer instances of gestational diabetes. There were no differences in any other characteristics between the physically active and inactive women, including blood pressure levels, modes of delivery, gestational weeks at delivery, birth weights and small for gestational age fetuses (birth weights below −2.0 standard deviation [SD] units, according to Finnish standards).
Table 2. Maternal and perinatal characteristics according to physical activity category in the FINNPEC.
3.3. Angiogenic markers in PE and non-PE women according to physical activity
Both first trimester serum samples and the questionnaire data on physical activity were available from 160 PE women and 160 non-PE women, and second/third trimester serum samples and questionnaire data on physical activity were available from 139 PE women and 47 non-PE women. The maternal and perinatal characteristics of the subsets of PE and non-PE women with first and second/third trimester serum samples of angiogenic markers are presented in Supplementary Table 1. In these subsets the PE women had higher blood pressure, higher rates of thrombocytopenia, delivered earlier and had infants of lower birth weight than the non-PE women. The maternal and perinatal characteristics of the whole cohort of the FINNPEC women, with available questionnaire data including 708 PE women and 724 non-PE women, are presented in Supplementary Table 2. The PE women in the whole cohort had higher BMI and higher rates of gestational diabetes and placental insufficiency compared to non-PE women. In the subsets of women with serum samples, there were no similar differences between the groups.
The first and second/third trimester serum concentrations of angiogenic markers in the PE and non-PE women according physical activity are presented in . There were no differences in the concentrations of angiogenic markers between the groups who exercised more or less than 2 − 3 times/week. Physical activity was not associated with the concentrations of angiogenic markers. The same analyses were done using the variable ‘Do you exercise ≥ 2–3 times/week, ≥ 30 min at a time with at least moderate intensity?’ with similar results (data not shown).
Table 3. Concentrations of angiogenic markers in PE and non-PE women according to physical activity category, mean estimate/model-based mean (95% CI).
4. Discussion
We found no differences in the physical activity and exercise habits between the PE and non-PE women in the FINNPEC cohort. A minority of the women, 43.4% of PE women and 42.4% of non-PE women, were classified as physically active. Further, we found no associations between physical activity in PE or non-PE women and the maternal serum concentrations of sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio.
4.1. Effects of physical activity on PE
There is literature in support of a protective role of physical activity on the incidence of PE, but the data are conflicting. In a systematic review and meta-analysis from 2018, a sensitivity analysis of 16 randomized controlled trials (RCTs) showed that prenatal exercise interventions had reduced the odds of developing PE by 41% [Citation4]. Moreover, some earlier systematic reviews and meta-analyses have reported that prenatal physical activity is related to lower incidence of PE [Citation5–7]. Yet, some recent systematic reviews and meta-analyses have found no association between PE and physical activity during pregnancy [Citation8–10, Citation23, Citation24]. In a recent systematic review and meta-analysis from 2022, Danielli et al. showed that supervised exercise during pregnancy reduced the risk of developing hypertensive disorders of pregnancy but not independently the risk of PE [Citation24]. An umbrella review of RCTs and updated meta-analysis from 2023 also supports the understanding that exercise during pregnancy does not reduce the incidence of PE [Citation10]. Moreover, the Cochrane review in 2015, evaluating the effectiveness of exercise interventions for preventing excessive weight gain during pregnancy and associated pregnancy complications, did not find any association between PE and exercise interventions [Citation25]. The inconsistency of the study results concerning the association of PE and prenatal exercise may be partly due to the different methods used in the studies to assess physical activity. Moreover, differences in the characteristics of pregnant women and insufficient statistical powers may also be behind the mixed results of the studies [Citation10, Citation23].
We found no differences in the reported physical activity and exercise habits between the PE and non-PE women. Self-reported information gained through questionnaires is prone to a recall bias, which might have affected our results. Further, the women reported about their average exercise habits during pregnancy, which may have varied from their exercise habits before pregnancy. In their meta-analysis, Davenport et al. stated that to achieve at least a 25% reduction in the odds of developing PE, pregnant women must accumulate at least 140 min of moderate-intensity exercise (brisk walking, water aerobics, stationary cycling or resistance training)/week [Citation4]. Our questionnaire data on physical activity did not allow us to evaluate the amount or intensity of weekly exercise comparably.
4.2. Effects of physical activity and PE on angiogenic markers
Increased plasma sFlt-1 levels after acute exercise have been observed in nonpregnant women [Citation15, Citation26] and in men [Citation27, Citation28] in a few small studies. The effect of regular exercise has been studied even less. Weissgerber et al. (2010) demonstrated that regular exercise was not associated with sFlt-1, sEng, PlGF or vascular endothelial growth factor (VEGF) concentrations in nonpregnant women [Citation15].
There is very limited data on the association of angiogenic markers and exercise in pregnant women. To our knowledge, this is the first study to investigate the association of physical activity in pregnancy and concentrations of angiogenic markers comparing pregnant PE women with non-PE women. In the current study, we showed that physical activity did not affect the concentrations of angiogenic markers in either PE or non-PE women. Previously, angiogenic markers have been shown to be expressed differently in pregnant women who exercise regularly than in those who do not [Citation15]. Contrary to our results, a cross-sectional study including 25 pregnant women reported higher serum PlGF and lower sFlt-1 and sEng concentrations in the third trimester in physically active pregnant women [Citation15]. Similar to our study, Weissgerber et al. [Citation15] used self-reported questionnaires to define the exercise habits of participants. Yet, the definitions of physically active differed: ours was exercising 2 − 3 times/week or more or exercising ≥ 2–3 times/week, ≥ 30 min at a time with at least moderate intensity, whereas Weissgerber et al. defined it as ‘exercising for at least 3 h/week at an intensity that is sufficient to cause sweating’. Further, the sample size in the Weissgerber et al. study was small compared to the present study.
Previously, rodent studies have investigated the association of exercise training and angiogenic markers in PE. A rat model of hypertension during PE and a rat model of PE superimposed on chronic hypertension showed that exercise training in pregnancy decreased sFlt-1 levels [Citation16, Citation17]. Contrary to these results, we found no association between physical activity and angiogenic markers in PE women. Gilbert et al. showed that exercise training before and during pregnancy stimulates a pro-angiogenic state/lowers sFlt-1 and increases vascular endothelial growth factor (VEGF) levels in rats [Citation16]. They stated that it remains unclear whether regular exercise training prior to pregnancy was important to their observations. Both pregnancy and exercise can be considerable physiological stressors. Pre-pregnancy exercise status was hypothesized to play a role in whether or not exercise during pregnancy is effective and safe as a preventive measure for increased blood pressure in pregnancy [Citation16]. Our study did not include physical activity before pregnancy, which might have influenced the results.
Enhanced placental growth and vascularity, reduced oxidative stress, reduced inflammation and correction of disease-related endothelial dysfunction have been proposed as the mechanisms behind the protective effect of exercise on developing PE [Citation11]. Further, exercise during pregnancy may promote a pro-angiogenic state [Citation15, Citation29]. In PE, circulating maternal serum levels of s-Flt-1 and sEng and sFlt-1/PlGF ratio are increased and levels of PlGF are decreased [Citation13, Citation14]. Equally, in the FINNPEC cohort, the serum concentrations of PlGF and endoglin and the sFlt-1/PlGF ratio were increased in PE women as compared to non-PE women and the serum concentrations of sFlt-1 were increased only at the second/third trimester in PE women [Citation30].
The main strength of this study is that it uses a nationwide, population-based cohort with detailed clinical information from medical records. Self-reported information obtained through questionnaires is prone to recall bias, which can be considered as a limitation. More objective measuring tools, such as pedometers or activity trackers, would be useful in future studies. The inter-individual variations in the serum concentrations of the angiogenic markers were relatively large and the sample size was small, especially when further dividing the study population into subcategories according to exercise status. Moreover, there was a much smaller number of second/third trimester serum samples available from the non-PE women (n = 47) compared with PE women (n = 139). We acknowledge the need for conducting additional research encompassing larger sample sizes.
5. Conclusions
In summary, maternal physical activity during pregnancy was not associated with PE in the FINNPEC cohort. In addition, physical activity of pregnant women with and without PE was not associated with the maternal serum concentrations of angiogenic markers sFlt-1, PlGF and sEng and sFlt-1/PlGF ratio.
The Finnish Genetics of Pre-eclampsia Consortium (FINNPEC) core investigator group
Hannele Laivuori, principal investigator, Medical and Clinical Genetics, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Institute for Molecular Medicine Finland, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland; Department of Obstetrics and Gynecology, Tampere University Hospital and Tampere University, Faculty of Medicine and Health Technology, Center for Child, Adolescent, and Maternal Health, Tampere, Finland.
Seppo Heinonen, Obstetrics and Gynecology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
Eero Kajantie, PEDEGO Research Unit, Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland; Public Health Promotion Unit, National Institute for Health and Welfare, Helsinki and Oulu, Finland; Children’s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Department of Clinical and Molecular Medicine, Norwegian University of Health and Technology, Trondheim, Norway.
Juha Kere, Department of Biosciences and Nutrition, Karolinska Institutet, Huddinge, Sweden; Folkhälsan Research Center and Stem Cells and Metabolism Research Program, University of Helsinki, Helsinki, Finland.
Katja Kivinen, Institute for Molecular Medicine Finland, Helsinki Institute of Life Science, University of Helsinki, Helsinki, Finland.
Anneli Pouta, Department of Government Services, National Institute for Health and Welfare, Helsinki, Finland.
Authors contributions
NJ, TJ, EE, and HL designed the research. The FINNPEC core investigator group established the study cohort. NJ analyzed the data. NJ wrote the first draft of the manuscript. TJ, EE, and HL contributed to the data analysis and interpretation and revised the manuscript. All authors read and approved the final manuscript.
| Abbreviations | ||
| BMI | = | Body mass index |
| FINNPEC | = | Finnish Genetics of Pre-eclampsia Consortium |
| PE | = | Preeclampsia |
| PlGF | = | Placental growth factor |
| RCT | = | Randomized controlled trial |
| sFlt-1 | = | Soluble fms-like tyrosine kinase 1 |
| sEng | = | Soluble endoglin |
Supplemental Material
Download MS Word (24.7 KB)Acknowledgements
We appreciate the expert technical assistance of Eija Kortelainen and the contributions of the members and assisting personnel of the FINNPEC Study Group.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
The authors confirm that some access restrictions apply to the data. The researchers interested in using the data must obtain approval from the FINNPEC Board (steering committee). The researchers using the data are required to follow the terms of a number of clauses designed to ensure the protection of privacy and compliance with relevant Finnish laws. Data requests may be subject to further review by the Ethics Committee and may also be subject to individual participant consent.
Additional information
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References
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