The risk of miscarriage after COVID-19 vaccination before and during pregnancy

Pregnant women are at higher risk of severe illness and adverse pregnancy outcomes due to a SARS-CoV-2 infection, which can be prevented by vaccination. Observational studies are needed to ascertain the safety of COVID-19 vaccination during pregnancy. We aimed to determine whether COVID-19 vaccination before and during pregnancy is associated with the risk of miscarriage.

In this cohort study, we included 4640 pregnant women (mean age: 32.8 ± 3.7 years) from the Dutch Pregnancy Drug Register between February 2021 and August 2022. Information on COVID-19 vaccinations, miscarriage, and confounders was self-reported, using web-based questionnaires. The hazard ratio (HR) of miscarriage (in gestational weeks 6-20) after a COVID-19 vaccination, was estimated using the survival analyses. A COVID-19 vaccination during pregnancy (≥1 COVID-19 vaccination between week 2 and 20 of pregnancy) was included as a time-dependent exposure and vaccination prior to pregnancy was included as a binary exposure.

A total of 3202 pregnant women (69%) received ≥1 COVID-19 vaccine in gestational week 2-20. We observed no association of vaccination during pregnancy with the risk of miscarriage (adjusted HR = 1.29, 95% CI = 0.93-1.74). Vaccination prior to pregnancy, however, was associated with a decreased risk of miscarriage (adjusted HR = 0.69, 95% CI = 0.48-0.99).

We demonstrated that COVID-19 vaccination during pregnancy is not associated with an increased risk of miscarriage in gestational weeks 6-20. This study adds to the growing body of evidence demonstrating the safety of COVID-19 vaccination during pregnancy.