Association of inactivated COVID-19 vaccination with maternal coagulation function in early pregnancy

Reports of rare but severe thrombotic events after receiving some COVID-19 vaccines brought concerns for the possibility of vaccine-induced coagulation abnormality. However, no study has reported the impacts of COVID-19 vaccination on coagulation function in pregnant women. We aimed to explore whether vaccination with inactivated COVID-19 vaccines before pregnancy was associated with coagulation changes in pregnant women. We conducted a retrospective cohort study in a tertiary-care hospital in Shanghai, China. A total of 5166 pregnant women were included, of whom 2721 (52.7%) completed vaccination before conception. Compared with unvaccinated women, the mean serum levels of prothrombin time (PT) and fibrinogen (FIB) were lower in vaccinated women by 0.09 (β = -0.09, 95% confidence interval [CI], -0.13, -0.05) mg/L and 0.11 (β = -0.11, 95% CI, -0.15, -0.07) mg/L, and the mean D-Dimer (D-D) levels were higher by 0.12 (β = 0.12, 95% CI, 0.09, 0.15) mg/L. However, no significant association was observed between COVID-19 vaccination and serum levels of activated partial thromboplastin time (APTT), fibrinogen degradation product (FDP) or thrombin time (TT). Our findings suggested that inactivated COVID-19 vaccination before conception resulted in a small change in maternal coagulation function, but this might not have clinical significance.