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Observational Study
. 2025 Jul 1;25(1):875.
doi: 10.1186/s12879-025-11225-6.

Placental transfer of SARS-CoV-2 antibodies in mother-neonate pairs: a prospective nested cohort study

Alex G Mugo  1 , Angela Koech  2   3 , Liberty Cantrell  4 , Moses Mukhanya  2 , Isaac Mwaniki  2 , Joseph Mutunga  2 , Merryn Voysey  4 , Rachel Craik  5 , Peter von Dadelszen  5   6 , Kirsty Le Doare  7 , Marleen Temmerman  2   3   6 , Geoffrey Omuse  8 ; periCOVID-Africa; PRECISE Network
Collaborators, Affiliations
Observational Study

Placental transfer of SARS-CoV-2 antibodies in mother-neonate pairs: a prospective nested cohort study

Alex G Mugo et al. BMC Infect Dis. .

Abstract

Background: Newborns depend on the transfer of IgG across the placenta to acquire protection against pathogens. We assessed the placental transfer of SARS-CoV-2 antibodies, primarily derived from infection, from seropositive pregnant women enrolled in a pregnancy cohort in Kilifi, Kenya.

Methods: The study was nested within a prospective observational multi-country cohort study. All available paired maternal delivery and cord blood samples were selected. Maternal sera were tested for SARS-CoV-2 receptor binding domain (RBD) IgM/IgG total antibodies using the Wantai assay. For positive samples, maternal and corresponding cord blood samples were tested for SARS-CoV-2 IgG antibodies against the spike (anti-spike) and nucleocapsid proteins (anti-NCP) using ELISA kits from Euroimmun.

Results: A total of 492 (56.1%) out of 877 maternal delivery samples were positive for RBD IgM/IgG total antibodies. Of these, 416 (84.6%) were seropositive for either anti-NCP IgG, anti-spike IgG antibodies or both. A total of 412 out of 496 (83%) cord blood samples tested positive for either anti-NCP or anti-spike antibodies. The geometric mean ratio was 1.04 (95% CI: 0.90, 1.21), indicating no significant difference between the anti-spike IgG concentration in cord and maternal blood samples. The log-transformed maternal and cord blood anti-spike IgG concentrations showed a weak positive correlation (r = 0.364, n = 496, p < 0.001). No maternal or neonatal factors were associated with the anti-spike IgG placental transfer ratio.

Conclusion: Placental transfer of SARS-CoV-2 antibodies was evident in a population of pregnant women whose immunity was primarily derived from infection given the low SARS-CoV-2 vaccine coverage in the study area. The positive correlation between maternal and cord blood anti-spike concentrations suggests that interventions that increase maternal antibody concentrations such as vaccination may increase passive immunity and protection against severe COVID-19 disease in neonates.

Keywords: COVID-19; Efficiency; Placental transfer; SARS-CoV-2 antibodies; Seropositivity.

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Conflict of interest statement

Declarations. Ethics approval and consent to participate: All participants provided written informed consent to participate in the PRECISE study including biological sample collection and storage and use of the data and samples for future research. The study was approved by the Aga Khan University Ethics Review Committee (2018/REC-74) and King’s College London BDM Research Ethics Subcommittee (Ref HR-17/18–7855. This study adhered to the ethical principles outlined in the Declaration of Helsinki. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Study flow diagram showing sample selection for analysis
Fig. 2
Fig. 2
Maternal and cord blood seropositivity for anti-NCP IgG and anti-spike (anti-S) IgG. Key: Seropositivity of maternal (left) and cord (right) samples for either anti-NCP IgG or anti-spike IgG or both. Seropositivity against anti-NCP IgG alone (light blue), anti-spike IgG alone (green), and both antigens (aqua green)
Fig. 3
Fig. 3
Placental transfer of anti-spike IgG for each mother-infant pair. Each point represents the placental transfer for one mother-infant pair. The boxplot shows the median and inter-quartile range
Fig. 4
Fig. 4
Paired maternal and cord blood anti-spike IgG concentrations. Points show the anti-spike IgG concentration in each maternal and cord blood sample, and the lines connect the anti-spike IgG concentration for each mother-infant pair. The boxplots show the median and inter-quartile range
See this image and copyright information in PMC

References

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