Background: Pregnant women and their neonates represent two vulnerable populations highly susceptible to viral infections with an interdependent immune system. The immune response of pregnant women to SARS-CoV-2 and the interplay of how the maternal immune response affects neonatal passive immunity have not been systematically studied.
Objectives: We characterized the serologic response in pregnant women and studied how this serologic response correlates with maternal clinical presentation and with the rate and level of passive immunity from mothers to neonates.
Study design: Between March 22-May 31, 2020, women giving birth who tested positive for semi-quantitative IgM or IgG detection in a New York City Hospital were included in the study. Retrospective chart review of the cases that met inclusion criteria was conducted for presence of COVID19 symptoms and use of oxygen support. Serology levels between the symptomatic and asymptomatic patients were compared with Welch’s two sample t-test. Further chart review of the same patient cohort was conducted in order to identify dates of self-reported onset of COVID-19 symptoms, and the timing of the peak of IgM and IgG antibody levels after symptoms onset were visualized using local polynomial regression smoothing (LOESS) on log2-scaled serological values. To study the neonatal serology response, cord blood samples of neonates born to a subset of all serology positive pregnant women were tested for serology. Maternal antibody levels of serology-positive vs. serology-negative neonates were compared with the Welch’s two sample t-test. The relationship between quantitative maternal and quantitative neonatal serologic data was studied using Pearson correlation and linear regression. Multiple linear regression analysis was conducted using maternal symptoms, maternal serology levels, and maternal use of oxygen support to determine predictors of neonatal IgG levels.
Results: Eighty-eight serology positive pregnant women were included in this study. Antibody levels are higher in symptomatic pregnant women compared to asymptomatic pregnant women. Serology studies in 34 women with symptom onset data reveal that maternal IgM and IgG levels peak around 15 and 30 days post COVID-19 symptoms onset, respectively. Furthermore, studies of fifty neonates born to a subset of serology positive women show that passive immunity in the form of IgG is conferred upon 78% of all neonates. Presence of passive immunity is dependent on maternal antibody levels, and levels of neonatal IgG correlate with maternal IgG levels. Maternal IgG levels and maternal use of oxygen support were predictive of neonatal IgG levels.
Conclusions: We demonstrate that maternal serologies correlate with symptomatic maternal infection, and higher levels of maternal antibodies are associated with passive immunity. Maternal IgG levels and maternal use of oxygen support, a marker of disease severity, predict neonatal IgG levels. These data will further guide the screening for this unique linked population of mothers and their babies, and can aid in developing maternal vaccination strategies.