Results
Among the 79 women who participated in the study, 72 had available
serology test results. Seven women did not have serology information due
to technical reasons. Thirty six neonates did not undergo nasopharyngeal
swabbing for SARS-CoV-2 PCR due to parental refusal. One woman did not
have enough serum to determine anti-spike IgM levels.
Patient characteristics are presented in Table 2. SARS-CoV-2 antibody
profiles of women who had COVID-19 during pregnancy and of their
neonates, are presented in Table 2. Among the 72 women, 36 (50%), 39
(54%) and 30 (42%) women tested positive for anti-spike-IgM,
anti-spike-IgG and anti-nucleocapsid-IgG, respectively
(p<0.0001 for the comparison of IgG antibodies; Table 3). At
least 8/72 (11%) neonates were infected with SARS-CoV-2 in utero; one
neonate had a positive PCR test and 7/48 neonates carried
anti-SARS-CoV-2 IgG while the mothers were sero-negative for the same
IgG. The rest of the neonates were either seronegative or had the same
IgG as their mothers, and therefore whether the IgG transferred from the
mothers or was self-produced by the fetus could not be determined. Of
the seronegative women for whom vertical transmission was identified,
8/48 (17%) neonates were infected with SARS-CoV-2 in utero. No fetal
malformations were detected.
Anti-nucleocapsid-IgG and anti-spike-IgG were detected in 83% and 85%
of neonates of mothers seropositive for those antibodies, respectively.
Maternal and neonatal IgG antibody levels were positively correlated
(Pearson coefficient 0.8, p<0.001). With regards to the
interval between infection and delivery, the highest rate of maternal
positive serology tests was when the interval was between 8-12 weeks
(89% anti-spike IgG, 78% anti-spike IgM and 67% anti-nucleocapsid
IgG). Thereafter, the rate of positive serology tests declined
gradually. After 20 weeks, only anti-spike IgG was detected in 33-50%
(Figure 1A).
Maternal anti-spike-IgG responses were the longest compared with
anti-nucleocapsid-IgG and anti-spike-IgM responses (Figure 1,B).
The rate of women with positive IgG serology was higher if COVID-19 was
symptomatic compared to asymptomatic (anti-nucleocapsid-IgG 29 (50%)
versus 1 (7%), p=0.004; anti-spike-IgG 35 (60%) versus 4 (29%),
respectively, p=0.03).