Background In Benin, as of April 12, 2023, 28,014 cases and 163 deaths of coronavirus disease (COVID-19) had been notified. COVID-19 disease has been associated with an increased risk of preterm birth, caesarean delivery and maternal morbidity. However, few studies have evaluated the extent of SARS-CoV-2 infection among pregnant women in sub-Saharan African countries. In this EDCTP-funded COVID-19 surveillance project, we aimed to determine SARS-CoV-2 seroprevalence and identify factors associated with seropositivity among pregnant women in Benin.

Methods A cross-sectional study was carried out between April and June 2022 in Allada, a middle-size city in southern Benin, and Natitingou, a city located 500 kilometres North. Pregnant women in their third trimester of pregnancy were recruited at study antenatal care clinics. A rapid diagnostic test for detection of IgG/IgM against the receptor binding domain of SARS-CoV-2 spike protein was performed, and socio-demographic and clinical characteristics of the participants were recorded.

Results A total of 861 women were included in the study. Mean age of study participants was 26.4 years, and their mean gestational age was 35.0 weeks. SARS-CoV-2 antibodies were detected in 75.7% (95%CI 75.6%-78.6%) of non-vaccinated participants. Only 6.7% (95%CI 5.15–8.62%) of the participants reported to had been vaccinated against COVID-19. Unvaccinated participants from Allada who had at least one previous morbidity had an almost three-fold increased risk of presenting SARS-CoV-2 antibodies (OR=2.89 [1.19–7.00]). None of the participants had been diagnosed/tested for COVID-19 during their pregnancy.

Conclusion The SARS-CoV-2 virus has circulated greatly among pregnant women from Benin. Despite none of the participants had been diagnosed with COVID-19, three out of four participants presented SARS-CoV-2 antibodies, suggesting that COVID-19 cases were asymptomatic or remained undetected by the national surveillance systems.