Maternal-Fetal Outcomes and Antibody Transfer, Depending on the Trimester of SARS-CoV-2 Infection in Non-Vaccinated Women—A Danish Nationwide Prospective Cohort Study

Passive maternal-fetal transfer of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies has been demonstrated, whilst the degree of transfer depending on the trimester of infection is lacking. Due to neonates’ immature immune systems, this knowledge could be of interest when investigating the degree of early-life protection against SARS-CoV-2. For perinatal infections such as Rubella and Toxoplasmosis, the timing of infection related to gestational age is crucial for the severity of maternal-fetal outcomes; hence, the trimester of SARS-CoV-2 infection could potentially be crucial. So far, there is no stratification on all three trimesters of SARS-CoV-2 infection in relation to maternal antibody levels in SARS-CoV-2 positive women, and the degree of transfer of SARS-CoV-2 antibodies to the newborn nor on obstetric and neonatal outcomes, which we examined in this study. Eleven departments in Denmark invited women who tested SARS-CoV-2 positive during pregnancy to participate with a blood sample and a cord blood sample at delivery. 459 SARS-CoV-2 positive women and 2567 SARS-CoV-2 negative women were included. A percentage of 87.5%, 95.3%, and 60.3% of newborns of women who tested positive in their first, second, and third trimester, respectively, had a significantly higher immunoglobin G (IgG) antibody level than their mother at delivery, indicating that the fetus is able to concentrate antibody levels or maintain the level of IgG antibodies transferred. None of the examined maternal-fetal outcomes were increased in women infected with SARS-CoV-2.