Factors influencing SARS-CoV-2 placental antibody transfer and neonatal transmission. A prospective, cohort study and review of available literature.

OBJECTIVE

To describe SARS-CoV-2 serologic status, associated factors, and neonatal transmission following gestational COVID-19.

STUDY

DESIGN

Prospective cohort study including neonates born to mothers with gestational COVID-19 at Hospital del Mar (Barcelona) between March 2020 and May 2022.

RESULTS

A total of 263 infants and 261 mothers were included. High seropositivity was observed in infected mothers (88.9%) and their newborns (82.8%), particularly following early gestational and mild-to-moderate infections and among vaccinated mothers. Higher placental antibody transfer ratios were observed in earlier maternal infections. However, a longer infection-to-delivery interval increased transfer ratios only for anti-nucleocapsid antibodies. Neonatal antibodies persisted for at least six months. Only 6.1% of neonates born to mothers with active infection tested positive, with no evidence of congenital transmission.

CONCLUSIONS

SARS-CoV-2 antibody placental transfer is frequent and efficient, conferring passive immunity during the first six months of life. Neonatal infection rate was low and attributable to horizontal transmission.