For a study, researchers sought to determine the peripartum consequences of COVID-19 immunization during pregnancy. A birth registry connected with the provincial COVID-19 vaccination database was used in a population-based retrospective cohort research in Ontario, Canada. All births occurred between December 14, 2020, and September 30, 2021. COVID-19 immunization during pregnancy, COVID-19 immunization after pregnancy, and no immunization Postpartum hemorrhage, chorioamnionitis, cesarean birth (including elective and emergency cesarean delivery), neonatal intensive care unit (NICU) admission, and poor infant 5-minute Apgar score (7) Linear and robust Poisson regression were used to calculate adjusted risk differences (aRDs) and risk ratios (aRRs) when comparing the cumulative incidence of outcomes in those who received COVID-19 vaccination during pregnancy to those who were vaccinated after pregnancy and those who had no record of COVID-19 vaccination at any point. To account for confounding, inverse probability of treatment weights were utilized.

About 22,660 (23%) of 97,590 people (mean [SD] age, 31.9 [4.9]) got at least one dose of COVID-19 vaccination during pregnancy (63.% received dose 1 in the third trimester; 99.8% received an mRNA vaccine). When those vaccinated during pregnancy were compared to those vaccinated after pregnancy (n=44,815), there were no significantly increased risks of postpartum hemorrhage (incidence: 3.0% vs 3.0% ; aRD, 0.28 per 100 individuals [95% CI, 0.59 to 0.03]; aRR, 0.91 [95% CI, 0.82-1.02]), chorioamnionitis (0.5% vs 0.5%; aRD, −0.04 per 100 individuals [95% CI, −0.17 to 0.09]; aRR, 0.92 [95% CI, 0.70-1.21]), cesarean delivery (30.8% vs 32.2%; aRD, −2.73 per 100 individuals [95% CI, −3.59 to −1.88]; aRR, 0.92 [95% CI, 0.89-0.95]), NICU admission (11.0% vs 13.3%; aRD, −1.89 per 100 newborns [95% CI, −2.49 to −1.30]; aRR, 0.85 [95% CI, 0.80-0.90]), or low Apgar score (1.8% vs 2.0%; aRD, −0.31 per 100 newborns [95% CI, −0.56 to −0.06]; aRR, 0.84 [95% CI, 0.73-0.97]). When compared to individuals who did not receive COVID-19 vaccination at any point (n = 30,115), the findings were qualitatively similar.

COVID-19 immunization during pregnancy, compared to vaccination after pregnancy and no vaccination, was not related with a higher risk of unfavorable peripartum outcomes in the population-based cohort analysis in Ontario, Canada. The study’s analysis should take into account that the immunizations received during pregnancy were mostly mRNA vaccines given in the second and third trimesters.