(168) Assessing Maternal and Fetal SARS-COV-2 Viral Load, Antibody Profiles and Placental Pathology Following Prenatal Infection

Evaluate the mother-to-infant transmission of SARS-CoV-2 and antibody transfer patterns following prenatal infection.


Study Design: Prospective cohort study of pregnant individuals in Ontario, Canada with COVID-19 in pregnancy. Sample collection at delivery included maternal swabs (nasopharyngeal/oropharyngeal, vaginal, anorectal), blood, breastmilk, newborn swab (nasopharyngeal, sub-amniotic), amniotic fluid, cord blood and placenta. Samples were analyzed by qPCR for SARS-CoV-2 RNA and IgG assays targeting the SARS-CoV-2 spike (S), nucleocapsid (N) and receptor binding domain (RBD) proteins. Placentas were evaluated for frequency and type of histologic lesions.

Results: The cohort included 213 individuals diagnosed with SARS-CoV-2 infection during pregnancy between Mar-2020 and Aug-2021, and their 215 exposed newborns. Median gestational age at COVID-19 diagnosis was 30.1 weeks (IQR 14.4). Most infections were mild (70.4%) and symptomatic (77.5%). A total 64/144 (44.8%) participants had active SARS-CoV-2 infections at delivery, as did 21/142 (14.8%) newborns. SARS-CoV-2 was also evident in vaginal (3/182), anorectal (5/175), sub-amniotic (1/165), breastmilk (1/38) and amniotic fluid (3/77) samples. A total of 118/193 (61.1%) maternal and 138/189 (73%) cord serum samples were positive for IgG COVID-19 antibodies. Maternal and cord serum anti-RBD, anti-N and anti-S IgG were significantly and positively correlated (R=0.26, 0.24, 0.23, respectively; p< 0.05 for all). The antibody transfer ratio of anti-RBD was significantly correlated with the number of weeks since maternal infection during pregnancy (R=0.28, p< 0.05). SARS-CoV-2 was detected in 6/138 (4.3%) placentas; placentas were characterized by acute (33/113) and chronic inflammation (20/113), and maternal (39/113) and fetal (12/113) vascular malperfusion.

Conclusion:

In this cohort, the rate of SARS-CoV-2 vertical transmission and transfer of maternal antibodies to newborn was high. Further investigation into the circumstances in which vertical transmission of SARS-CoV-2 occurs and its implication on maternal-fetal antibody transfer is needed.