Comparatively low rates of COVID-19 in women admitted in labor and their newborns prior to routine vaccination of pregnant women: insights from Denmark

Abstract

Background: In a country with a high-test frequency, societal lockdown, and pregnancy leave granted from 28 gestational weeks, we investigated SARS-CoV-2 infection in women admitted in labor and their newborn in the pre-vaccine period.

Material and methods: A total of 1042 women admitted for delivery in two Danish hospitals agreed to a plasma sample and nasopharyngeal, vaginal, and rectal swabs and to sampling of umbilical cord blood and a nasopharyngeal swab from their newborn at delivery. Plasma samples from women were examined for SARS-CoV-2 antibodies. If antibodies were detected, or the woman had a positive nasopharyngeal swab upon admission or had a household contact with symptoms consistent with COVID-19, SARS-CoV-2 PCR was performed on plasma and swab samples from mother and child.

Results: Seventeen women (1.6%) were seropositive. Half the newborn (n = 9 (53%)) of seropositive mothers were also seropositive. None of the seropositive women or newborns had clinical signs of COVID-19 and all had SARS-CoV-2 PCR negative plasma and swab samples.

Conclusion: Adherence to specific national guidelines pertaining to testing, self-imposed isolation, and cautious behaviors among pregnant women likely contributed to the exceptionally low prevalence of both prior and current COVID-19 infections detected at the time of childbirth preceding the routine vaccination of pregnant women in Denmark.

Keywords:

• Infection
• isolation
• SARS-CoV-2
• transmission
• labor

Acknowledgements

The authors thank all the participants, the midwives and the laboratory technicians at Aarhus University Hospital and Lillebaelt Hospital and The Novo Nordisk Foundation. A special thank you to Lene Toft Nielsen, Lone Pødenphant, Camilla Andersen and Lene Yding for their tremendous effort in the logistics of inclusion, handling of samples and laboratory analysis.

Consent to participate

All women received oral and written information about the project. A video presentation of the project and the written material were available online to the women, and midwives provided information on the project at the antenatal visits and when the women were admitted for delivery. Written consent was obtained from all women, and from one or both parents on behalf of the newborn.

Ethical approval

The project was approved by the Danish Ethical Committee (S-20200045C), date of approval: April 2, 2020. GDPR permission 20/15901, date of approval: March 30, 2020.

Disclosure statement

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

Data availability statement

Raw data were generated at Research unit of OPEN – Open Patient Explorative Network, Denmark. Derived data supporting the findings of this study are available from the corresponding author SYN on request.

Additional information

Funding

The project received funding from Novo Nordisk Fonden [NNF20SA0062875]. The funder played no role in the conduction of research or writing of the manuscript.