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Association of COVID-19 Vaccination in Pregnancy With Adverse Peripartum Outcomes
Deshayne B Fell1,2, Tavleen Dhinsa2,3, Gillian D Alton2,3
1School of Epidemiology and Public Health, University of Ottawa, Ottawa, Ontario, Canada.
Insights
COVID-19 vaccination during pregnancy did not increase the risk of adverse peripartum outcomes like postpartum hemorrhage or cesarean delivery. This large Canadian study found no significant safety concerns for vaccinated pregnant individuals compared to those vaccinated after pregnancy or unvaccinated individuals.
Area of Science:
- Epidemiology
- Maternal-Fetal Medicine
- Vaccinology
Background:
- Limited comparative epidemiological data exists on COVID-19 vaccination outcomes during pregnancy.
- Large-scale monitoring of pregnancy and peripartum outcomes is crucial for public health.
- Understanding the safety of COVID-19 vaccines in pregnant populations is a priority.
Purpose of the Study:
- To evaluate peripartum outcomes in individuals who received COVID-19 vaccination during pregnancy.
- To compare adverse outcomes between pregnant individuals vaccinated during pregnancy versus after pregnancy, and those unvaccinated.
- To assess the safety profile of COVID-19 vaccines in a large, real-world obstetric cohort.
Main Methods:
- Population-based retrospective cohort study in Ontario, Canada (December 2020 - September 2021).
- Linked birth registry and provincial COVID-19 immunization database.
- Used regression models with inverse probability of treatment weights to compare outcomes including postpartum hemorrhage, chorioamnionitis, cesarean delivery, NICU admission, and low Apgar score.
Main Results:
- Among 97,590 individuals, 23% received COVID-19 vaccination during pregnancy (primarily mRNA vaccines).
- No significant increase in risks for postpartum hemorrhage, chorioamnionitis, cesarean delivery, NICU admission, or low Apgar score was observed when comparing vaccination during pregnancy versus after pregnancy.
- Findings were similar when compared to unvaccinated individuals.
Conclusions:
- COVID-19 vaccination during pregnancy is not associated with increased adverse peripartum outcomes.
- The study supports the safety of COVID-19 vaccination in pregnant individuals, particularly with mRNA vaccines in the second and third trimesters.
- Results provide important epidemiological evidence for clinical decision-making regarding vaccination in pregnancy.
Importance:
There is limited comparative epidemiological evidence on outcomes associated with COVID-19 vaccination during pregnancy; monitoring pregnancy outcomes in large populations is required.
Objective:
To evaluate peripartum outcomes following COVID-19 vaccination during pregnancy.
Design, Setting, And Participants:
Population-based retrospective cohort study in Ontario, Canada, using a birth registry linked with the provincial COVID-19 immunization database. All births between December 14, 2020, and September 30, 2021, were included.
Exposures:
COVID-19 vaccination during pregnancy, COVID-19 vaccination after pregnancy, and no vaccination.
Main Outcomes And Measures:
Postpartum hemorrhage, chorioamnionitis, cesarean delivery (overall and emergency cesarean delivery), admission to neonatal intensive care unit (NICU), and low newborn 5-minute Apgar score (<7). Linear and robust Poisson regression was used to generate adjusted risk differences (aRDs) and risk ratios (aRRs), respectively, comparing cumulative incidence of outcomes in those who received COVID-19 vaccination during pregnancy with those vaccinated after pregnancy and those with no record of COVID-19 vaccination at any point. Inverse probability of treatment weights were used to adjust for confounding.
Results:
Among 97 590 individuals (mean [SD] age, 31.9 [4.9] years), 22 660 (23%) received at least 1 dose of COVID-19 vaccine during pregnancy (63.6% received dose 1 in the third trimester; 99.8% received an mRNA vaccine). Comparing those vaccinated during vs 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]). Findings were qualitatively similar when compared with individuals who did not receive COVID-19 vaccination at any point (n = 30 115).
Conclusions And Relevance:
In this population-based cohort study in Ontario, Canada, COVID-19 vaccination during pregnancy, compared with vaccination after pregnancy and with no vaccination, was not significantly associated with increased risk of adverse peripartum outcomes. Study interpretation should consider that the vaccinations received during pregnancy were primarily mRNA vaccines administered in the second and third trimester.
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