Participants were classified as infected during pregnancy if their serological testing met one of two criteria; 1) Positive for anti-SARS-CoV-2 IgM antibodies at either the screening or delivery visit because IgM antibodies against SARS-COV-2 typically appear within the first few weeks of infection and persist for several weeks (29, 30) or 2) if participants seroconverted by IgG from negative at screening to positive at delivery or if the concentration of IgG antibodies at delivery was at least 3.5-fold higher than the concentration at screening. Here, CD40LG is linked to infection.