Comparison of Maternal IgG Antibody from Infected SARS-CoV-2 Mothers to Newborns in the 2nd and 3rd Trimesters: A Cohort Study

Background: No vertical transmission has been reported for Severe Acute Respiratory Syndrome (SARS-CoV-2); Yet, Immunoglobulin G (IgG) antibody was detected against SARS-CoV-2 amongst infants. The present study aimed to compare maternal IgG antibody concentration from infected SARS-CoV-2 mothers to newborns in the 2nd and 3rd trimesters. As a secondary outcome, the interval between the onset of infection and delivery and COVID-19 severity were compared.Methods: An observational cohort study was conducted on COVID-19 positive pregnant women in the 2nd and 3rd trimesters in Fars province, Iran between 21 March and 22 October 2021. A questionnaire was completed to record background characteristics of the study participants. Real-time Reverse Transcription Polymerase Chain Reaction tests were taken from newborns immediately after birth to diagnose COVID-19. Maternal and cord blood specimen were taken to measure IgG concentrations; generalized linear models were used to report the crude and adjusted Rate Ratios with 95% confidence interval (cRR and aRR (95% C.I)), and IBM SPSS Statistics version 22 was used, at the significance level of 0.05.Results: From 37 patients, 15 and 22 patients were in the 2nd and 3rd trimesters of pregnancy, respectively. After adjusting on maternal age, Cord IgG concentration was positively associated with maternal IgG concentration and interval between the onset of infection and delivery in the 3rd trimester (aRR (95% CI); 2.86 (2.27-3.6) and 1.23 (1.01-1.51)); however, no association was observed with COVID-19 severity (aRR (95% CI); 0.88 (0.09-8.66)). A positive association was also seen between high levels of cord IgG and maternal IgG (≥1.1 U/mL) (aRR (95% CI); 2.31 (1.05-5.09)). No significant associations were seen in the 2nd trimester of pregnancy (P 0.05 for all).Conclusions: In late pregnancy, Cord IgG concentration was positively associated with maternal IgG and interval between the onset of infection and delivery. Also, high levels of IgG antibody (≥1.1 U/mL) resulted in significantly higher level of cord IgG (≥1.1 U/mL).