Darine El-Chaar,Malia S.Q. Murphy,Alysha Dingwall-Harvey,Sheryll Dimanlig-Cruz,Stephanie T. Boyd,Ruth Rennicks White,Romina Fakhraei,Kathryn M. Denize,Corey Arnold,Marilyn Whelan,Jason Brophy,D. William J. Cameron,Deshayne B. Fell,Mark C. Walker,Barbra de Vrijer,Martin Pelchat,Marc André Langlois,
Assessing maternal and fetal SARS-CoV-2 viral load, antibody profiles and placental pathology following prenatal infection
Assessing maternal and fetal SARS-CoV-2 viral load, antibody profiles and placental pathology following prenatal infection

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

Prospective cohort of pregnant individuals infected with COVID-19. Samples collected at delivery included maternal swabs (nasopharyngeal/oropharyngeal, vaginal, anorectal), blood, breastmilk, newborn swabs (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 histologic lesions.

The cohort included 213 individuals who delivered between from March 2020 to August 2021, and their 215 exposed offspring. SARS-CoV-2 was evident in maternal nasopharyngeal (64/145), vaginal (3/184) and anorectal (5/182) swabs and breastmilk (1/38). A total of 27/212 infants (12.7%) demonstrated evidence of mother-to-child transmission of SARS-CoV-2; SARS-CoV-2 was detected in nasopharyngeal swabs (21/142), amniotic fluid (3/77), sub-amniotic swabs (1/165), and placenta homogenates (6/138). Anti-SARS-CoV-2 IgA and IgM were detected in 1/189 neonates. 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). Antibody transfer ratio of anti-RBD IgG was significantly correlated with weeks since maternal infection during pregnancy (R = 0.28, P <0.05). SARS-CoV-2 was detected in 6/138 placentas; placentas were characterized by acute (33/113), chronic inflammation (20/113), maternal (39/113) and fetal (12/113) vascular malperfusion.

The rate of SARS-CoV-2 vertical transmission and transfer of maternal antibodies to newborn tissues was high. There were no pathological differences between infected placentas and controls. Further investigation into the timing of vertical transmission is warranted and its potential implications on offspring outcomes.