Objective: To determine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in pregnancy in an inner-city setting and assess associations with demographic factors and vaccination timing. Design: Repeated cross-sectional surveillance study. Setting: London maternity centre. Sample: A total of 906 pregnant women attending nuchal scans, July 2020–January 2022. Methods: Blood samples were tested for IgG antibodies against SARS-CoV-2 nucleocapsid (N) and spike (S) proteins. Self-reported vaccination status and coronavirus disease 2019 (COVID-19) infection were recorded. Multivariable regression models determined demographic factors associated with seroprevalence and antibody titres. Main outcome measures: Immunoglobulin G N- and S-protein antibody titres. Results: Of the 960 women, 196 (20.4%) were SARS-CoV-2 seropositive from previous infection. Of these, 70 (35.7%) self-reported previous infection. Among unvaccinated women, women of black ethnic backgrounds were most likely to be SARS-CoV-2 seropositive (versus white adjusted risk ratio [aRR] 1.88, 95% CI 1.35–2.61, p < 0.001). Women from black and mixed ethnic backgrounds were least likely to have a history of vaccination with seropositivity to S-protein (versus white aRR 0.58, 95% CI 0.40–0.84, p = 0.004; aRR 0.56, 95% CI 0.34–0.92, p = 0.021, respectively). Double vaccinated, previously infected women had higher IgG S-protein antibody titres than unvaccinated, previously infected women (mean difference 4.76 fold-change, 95% CI 2.65–6.86, p < 0.001). Vaccination timing before versus during pregnancy did not affect IgG S-antibody titres (mean difference −0.28 fold-change, 95% CI −2.61 to 2.04, p = 0.785). Conclusions: This cross-sectional study demonstrates high rates of asymptomatic SARS-CoV-2 infection with women of black ethnic backgrounds having higher infection risk and lower vaccine uptake. SARS-CoV-2 antibody titres were highest among double-vaccinated, infected women.
- early pregnancy
- infectious disease
- maternity services
- medical disorders in pregnancy