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Peripartum Outcomes Following COVID-19 Vaccination in Late Pregnancy: Findings from a Population-Based Retrospective Cohort Study in Ontario, Canada

      Objectives

      Evaluate peripartum outcomes following COVID-19 vaccination during pregnancy.

      Methods

      Ontario population-based retrospective cohort between December 14, 2020 and September 30, 2021 using linkage of provincial birth registry and COVID-19 immunization databases. Poisson regression was used to generate risk ratios (RR) and 95% confidence intervals (CI), adjusted for temporal, socio-demographic, and clinical factors using propensity scores. Obstetric (postpartum hemorrhage, chorioamnionitis, cesarean birth) and newborn (NICU admission and 5-minute Apgar<7) outcomes were compared for those who received ≥1 dose of COVID-19 vaccine during pregnancy with 2 unexposed groups—Group 1: individuals vaccinated postpartum, Group 2: never vaccinated.

      Results

      Among 97 590 individuals, 22 660 (23%) received ≥1 dose of vaccine during pregnancy (64% received dose 1 in 3rd trimester). Compared with those vaccinated postpartum, we found no increased risks of postpartum hemorrhage (aRR 0.91, 95% CI 0.82–1.02); chorioamnionitis (aRR 0.92, 95% CI 0.70–1.21); or cesarean (aRR 0.92, 95% CI 0.89–0.95) following COVID-19 vaccination, nor any increased risk of NICU admission or 5-minute Apgar <7. All findings were similar when compared with individuals who did not receive COVID-19 vaccination at any point. We did not observe any difference according to vaccine product, number of doses received during pregnancy, or trimester of dose 1.

      Conclusions

      As of late 2021, there is limited evidence from comparative studies in large populations on outcomes following COVID-19 vaccination during pregnancy. Our study of births up to September 30, 2021 did not identify any increased adverse peripartum outcomes associated with later pregnancy COVID-19 vaccination. Once more individuals vaccinated earlier in pregnancy deliver, we will report on other important obstetric and perinatal outcomes.

      Keywords

      COVID-19 vaccine; pregnancy; epidemiology