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. 2024 May 21;24(1):509.
doi: 10.1186/s12879-024-09399-6.

Seroprevalence and placental transfer of SARS-CoV-2 antibodies in unvaccinated pregnant women

An Vercoutere  1 , Mbiton Joel Zina  2 , Meltem Telis  3 , Jean-Christophe Goffard  4 , Michel Boulvain  5 , Loïc de Doncker  6 , Sara Derisbourg  5 , Sylvie Houben  7 , Marie-Luce Delforge  8 , Caroline Daelemans #  9 , Dorottya Kelen #  3
Affiliations

Seroprevalence and placental transfer of SARS-CoV-2 antibodies in unvaccinated pregnant women

An Vercoutere et al. BMC Infect Dis. .

Abstract

Purpose: Pregnant women are at risk of severe SARS-CoV-2 infection, potentially leading to obstetric and neonatal complications. Placental transfer of antibodies directed to SARS-CoV-2 may be protective against neonatal COVID-19, but this remains to be studied. We aimed to determine the seroprevalence of SARS-CoV-2 antibodies in a population of unvaccinated pregnant women and to determine the placental transfer of these antibodies.

Methodology: A total of 1197 unvaccinated women with mostly unknown pre-study SARS-CoV-2 infection status, were tested at delivery for SARS-CoV-2 spike protein IgG antibodies during the first year of the pandemic. Umbilical cord samples were collected and assessed for seropositivity if the mother was seropositive. Maternal characteristics, pregnancy and neonatal outcomes and data on SARS-CoV-2 infection were extracted from medical records.

Results: Specific IgG were detected in 258 women (21.6%). A significant placental transfer to the newborn was observed in 81.3% of cases. The earlier in the 2nd and 3rd trimesters that the mother had contracted the disease and the more symptomatic she was, the greater the likelihood of transplacental transfer of IgG to her newborn.

Conclusion: Approximately one in five women had detectable anti-SARS-CoV-2 spike protein IgG antibodies at delivery during the first year of the pandemic, and these antibodies were significantly transferred to their fetuses. This research provides further evidence to better understand the dynamics of the placental transfer of SARS-CoV-2 IgG antibodies from mothers to their newborns, which is necessary to improve vaccination strategies.

Keywords: Antibody; COVID-19; Placental transfer; Pregnancy; SARS-COV-2 antibodies; Seroprevalence.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Flowchart representing detected antibodies in blood samples of participants. Abbreviations: IgM = immunoglobulin M; IgG = immunoglobulin G; UC = umbilical cord
Fig. 2
Fig. 2
Placental transfer ratio. a The box plot showing the placental transfer ratio of all cases. b Scatter plot illustrating the relationship between placental transfer ratio and gestational age (in weeks) at which a positive PCR was detected (focusing on the second and third trimesters only). c Scatter plot illustrating the relationship between placental transfer ratio and the number of days between birth and positive PCR test result
See this image and copyright information in PMC

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