A recent study of 283 pregnant women in China published recently in BMC Pregnancy and Childbirth showed mothers who contracted COVID-19 during pregnancy experienced no increased risk of complications, and their infants showed no signs of harm.
Researchers found that antibodies from infected mothers were passed to their newborns, potentially offering passive immunity for one to three months. These results suggest that reinfection during pregnancy may further strengthen this protection without causing adverse effects.
These results may reassure expectant mothers concerned about the effect of COVID-19 on their health and their babies’ well-being. This study also highlights the role of maternal immunity in neonatal health, including conditions such as fetal and neonatal alloimmune thrombocytopenia (FNAIT), which involves maternal antibodies affecting fetal platelets.
This study divided participants into five groups based on when they were infected and analyzed their antibody levels in plasma, umbilical cord blood, and breast milk. Researchers tracked maternal and neonatal outcomes through birth and at one, three, and six months postpartum. They found no significant differences in pregnancy complications, delivery methods, or neonatal health between infected and uninfected mothers. Notably, babies born to mothers infected at any stage of pregnancy had significantly lower rates of COVID-19 compared to those born to uninfected mothers.
“The study revealed an elevated risk of COVID-19 infection in infants who were not exposed to SARS-CoV-2 in utero, starting from one month of age,” explained the authors. They continued, “Particularly during the 1–3 month period, there was a significantly higher incidence of COVID-19 infection in infants born to non-infected mothers, which aligns with their diminished levels of antibodies at birth.”
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Mothers who had COVID-19 during pregnancy displayed higher immunoglobulin G antibody levels in both their blood and umbilical cord blood than uninfected mothers, indicating successful transfer of antibodies to their babies. The median antibody transfer ratio across all infected groups was 1.15, with no significant differences between trimesters. This suggests that regardless of when infection occurred, mothers provided similar levels of immune protection to their newborns.
Reinfection during pregnancy led to significantly higher immunoglobulin A (IgA) antibody levels, which are important for mucosal immunity. This was particularly evident in breast milk, where IgA levels in reinfected mothers were notably higher than in other groups. While IgA concentrations decreased one month postpartum, these results suggest that maternal reinfection could extend passive immunity to infants during their early months.
Newborns were monitored for growth, development, and infections. Although respiratory infections increased over time, babies of infected mothers—particularly those reinfected during pregnancy—had significantly lower infection rates than those born to uninfected mothers. No differences were observed in neurodevelopment, congenital heart defects, or other health markers. These results suggest that maternal infection may provide some degree of protection against early-life infections.
This study offers critical insights into maternal immunity and neonatal health in the context of COVID-19. Pregnant women who contract COVID-19, even more than once, are unlikely to experience complications, and their babies may benefit from passive immunity. These results provide valuable reassurance for expectant mothers and healthcare providers navigating pregnancy during the pandemic.
“We found that reinfection during pregnancy may not exhibit an elevated risk of adverse outcomes and confers a prolonged duration of passive immunity,” concluded the study.
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