Seroconversion of SARS-CoV-2 Antibodies in Pregnant Women During the Second Wave of the COVID-19 Pandemic in India: A Longitudinal Study

Aim This study aims to investigate the seroconversion of antibodies against SARS-CoV-2 infection in pregnant women during their first and third trimesters, specifically during the second wave of the COVID-19 pandemic. Methodology This is a longitudinal follow-up study of pregnant women during the second peak of the COVID-19 pandemic. Patients in their first trimester (six to 12 weeks) were tested for SARS-CoV-2 IgM and IgG levels, with a repeat test conducted in the third trimester (28-40 weeks) using the automated VIDAS® (bioMérieux SA, Marcy-l'Étoile, France) system. Samples were compared to assess seroconversion rates. Results In the current study, 120 of the 298 eligible women were followed through to the third trimester. Seroconversion of SARS-CoV-2 IgG from the first to third trimester was observed in 28 women (23.3%), including six women (21.4%) who developed SARS-CoV-2 IgG antibodies in the third trimester, and 22 women (78.5%) who were IgG positive in the first trimester but became IgG negative by the third trimester. Seroconversion of SARS-CoV-2 IgM from the first to third trimester was observed in 15 women (12.5%), of whom three women (25%) developed SARS-CoV-2 IgM antibodies in the third trimester, while 12 women (80%) who had these antibodies earlier no longer retained them by the third trimester. Conclusions The seroconversion rate during pregnancy is high, and natural immunity acquired through infection may not provide long-term protection, even over the course of the pregnancy.