According to a study in JAMA Pediatrics, coronavirus antibodies from a mother can cross the placenta, passing on some natural immunity to their newborns. Notably, the antibodies that scientists detected in the placenta were immunoglobulin G, or IgG, antibodies. These antibodies are made days after getting infected and are believed to offer some protection against the coronavirus.
Researchers tested more than 1,500 women who gave birth at a Philadelphia hospital, 83 of whom had COVID-19 antibodies, between April and August 2020. After giving birth, 72 of the 83 babies had antibodies in their umbilical cord blood. About half of the babies had antibody levels that were as high or higher than their mother’s blood levels, including about 25 percent with antibody levels nearly twice as high as their mother’s.
The researchers said that this could mean an earlier coronavirus inoculation might be better for pregnant women. “When vaccines are widely available, the optimal timing of maternal vaccination during pregnancy will need to consider maternal and fetal factors including the time needed to ensure neonatal protection,” the researchers stated. “The majority of women in our study who were seropositive [meaning they had detectable antibodies in their blood] were asymptomatic, with uncertain timing of viral exposure.”