Research interpretation
Approximately 50% of the mothers in our cohort had SARS-CoV-2 antibodies. In a study that examined 392 COVID-19 convalescent subjects, 366 (93.4%) were positive for SARS-CoV-2 IgG antibodies3. Time from positive SARS-CoV-2 nasopharyngeal swab correlated with SARS-CoV-2 IgG antibody levels (Pearson r –0.281, p < 0.001), with a 50% decline in antibody levels within 6 months; however, levels were still above the cut-off for positive serology result. Thereafter, antibody levels stabilized and remained similar up to 9 months post-infection. In 15% of participants with tests at two time points (N=59), SARS-CoV-2 anti-spike antibodies decreased below the positive cut-off3. According to our results, during pregnancy, anti-SARS-CoV-2 antibody titers declined more rapidly, with the rate of women with positive anti-spike IgG declining from 89% at 2-3 months post-infection to 38% by 5 months post-infection. These data suggest that while immune responses to SARS-CoV-2 infection during pregnancy are similar to those measured in non-pregnant women3, antibody titer decline more rapidly during pregnancy. One explanation is due to the transition to a Th2 anti-inflammatory environment during pregnancy that may attenuate the immune response23-25. Future studies should explore this hypothesis. This observation suggests that SARS-CoV-2 vaccination should be considered 3 months post-infection in pregnant women due to a decline in antibody levels.