Cord Blood SARS-CoV-2 IgG Antibodies and Their Association With Maternal Immunity and Neonatal Outcomes

Abstract

Passive transplacental immunity is crucial for neonatal protection from infections. Data on the correlation between neonatal immunity to SARS-CoV-2 and protection from adverse outcomes is scarce. This work aimed to describe neonatal seropositivity in the context of maternal SARS-CoV-2 infection, seropositivity, and neonatal outcomes. This retrospective nested case-control study enrolled high-risk pregnant women with a SARS-CoV-2 RT-PCR positive test who gave birth at the Instituto Nacional de Perinatología in Mexico City and their term neonates. Anti-SARS-CoV-2 IgG antibodies in maternal and cord blood samples were detected using a chemiluminescent assay. In total, 63 mother-neonate dyads (mean gestational age 38.4 weeks) were included. Transplacental transfer of SARS-CoV-2 IgG occurred in 76% of neonates from seropositive mothers. A positive association between maternal IgG levels and Cycle threshold (Ct) values of RT-qPCR test for SARS-CoV-2 with neonatal IgG levels was observed. Regarding neonatal outcomes, most seropositive neonates did not require any mechanical ventilation, and none developed any respiratory morbidity (either in the COVID-19 positive or negative groups) compared to 7 seronegative neonates. Furthermore, the odds of neonatal respiratory morbidity exhibited a tendency to decrease when neonatal IgG levels increase. These results add further evidence suggesting passive IgG transfer importance.