Seroprevalence of SARS-CoV-2 during pregnancy and associated outcomes: results from an ongoing prospective cohort study, New York City

Background: In May-July 2020 in the New York City area, up to 16% of pregnant women had reportedly been infected with SARS-CoV-2. Prior studies found associations between SARS-CoV-2 infection during pregnancy and certain adverse outcomes (e.g., preterm birth, cesarean delivery). These studies relied on reverse transcription polymerase chain reaction (RT-PCR) testing to establish SARS-CoV-2 infection. This led to overrepresentation of symptomatic or acutely ill cases in scientific studies. Objective: To expand our understanding of the effects of SARS-CoV-2 infection during pregnancy on pregnancy outcomes, regardless of symptomatology and stage of infection, by using serological tests to measure IgG antibody levels. Study Design: The Generation C Study is an ongoing prospective cohort study conducted at the Mount Sinai Health System. All pregnant women receiving obstetrical care at the Mount Sinai Hospital and Mount Sinai West Hospital from April 20, 2020 onwards are eligible for participation. For the current analysis, we included participants who had given birth to a liveborn singleton infant on or before August 15, 2020. Blood was drawn as part of routine clinical care; for each woman, we tested the latest sample available to establish seropositivity using a SARS-CoV-2 serologic enzyme-linked immunosorbent assay. Additionally, RT-PCR testing was performed on a nasopharyngeal swab taken during labor and delivery. Pregnancy outcomes of interest (i.e., gestational age at delivery, birth weight, mode of delivery, Apgar score, ICU/NICU admission, and neonatal hospital length of stay) and covariates were extracted from electronic medical records. Among all Generation C participants who had given birth by August 15, 2020 (n=708), we established the SARS-CoV-2 seroprevalence. Excluding women who tested RT-PCR positive at delivery, we conducted crude and adjusted linear and logistic regression models to compare antibody positive women without RT-PCR positivity at delivery with antibody negative women without RT-PCR positivity at delivery. We stratified analyses by race/ethnicity to examine potential effect modification. Results: The SARS-CoV-2 seroprevalence based on IgG measurement was 16.4% (n=116, 95% CI 13.7-19.3). Twelve women (1.7%) were SARS-CoV-2 RT-PCR positive at delivery (11 of these women were seropositive). Seropositive women were generally younger, more often Black or Hispanic, and more often had public insurance and higher pre-pregnancy BMI compared with seronegative women. SARS-CoV-2 seropositivity without RT-PCR positivity at delivery was associated with decreased odds of caesarean delivery (aOR 0.48, 95%CI 0.27; 0.84) compared with seronegative women without RT-PCR positivity at delivery. Stratified by race/ethnicity, the association between seropositivity and decreased odds of caesarean delivery remained for non-Hispanic Black/African-American and Hispanic women, but not for non-Hispanic White women. No other pregnancy outcomes differed by seropositivity, overall or stratified by race/ethnicity. Conclusion: Seropositivity for SARS-CoV-2 without RT-PCR positivity at delivery, suggesting that infection occurred earlier during pregnancy, was not associated with selected adverse maternal or neonatal outcomes among live births in a cohort sample of women from New York City. While non-Hispanic Black and Latina women in our cohort had a higher rate of SARS-CoV-2 seropositivity compared with non-Hispanic White women, we found no increase in adverse maternal or neonatal outcomes among these groups due to infection.