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.