Safety of COVID-19 vaccines among pregnant individuals in Quebec, Canada: a population-based retrospective cohort study from the Canadian Immunization Research Network
Bibliographic record
Abstract
OBJECTIVE: To estimate the association between maternal COVID-19 vaccination during pregnancy and adverse neonatal and maternal outcomes. DESIGN: Population-based retrospective cohort study using a hospitalisation database linked with other health administrative databases. SETTING: Province of Quebec, Canada, from 1 May 2021 to 30 June 2023. PARTICIPANTS: All singleton pregnancies resulting in a live birth or stillbirth at ≥20 weeks of gestation, excluding those with a conception date <42 weeks before the end of the study period. PRIMARY OUTCOME MEASURES: We used robust Poisson regression models to estimate adjusted risk ratios (aRRs) for chorioamnionitis, postpartum haemorrhage, caesarean delivery, preterm birth, very preterm birth, small for gestational age (SGA), maternal and neonatal admission to intensive care unit (ICU, NICU) and severe neonatal morbidity. We used a Cox regression model with a time-varying exposure variable to estimate adjusted HRs (aHRs) for stillbirth. Propensity score weighting was used to adjust for potential confounding. RESULTS: Among 140 073 singleton pregnancies resulting in live birth or stillbirth, 61 282 individuals (43.8%) received at least one dose of messenger RNA COVID-19 vaccine during pregnancy. Vaccination during pregnancy was not associated with an increased risk of chorioamnionitis (aRR 0.99, 95% CI 0.95 to 1.04), postpartum haemorrhage (aRR 1.03, 95% CI 0.99 to 1.06), very preterm birth (aRR 1.04, 95% CI 0.89 to 1.21) and stillbirth (aHR 1.14, 95% CI 0.94 to 1.39). Vaccination during pregnancy was significantly associated with a reduced risk of caesarean delivery (aRR 0.94, 95% CI 0.92 to 0.96), maternal ICU admission (aRR 0.80, 95% CI 0.65 to 0.98), SGA (aRR 0.94, 95% CI 0.91 to 0.98), NICU admission (aRR 0.91, 95% CI 0.85 to 0.96), preterm birth (aRR 0.94, 95% CI 0.90 to 0.99) and severe neonatal morbidity (aRR 0.91, 95% CI 0.85 to 0.98). CONCLUSIONS: Our findings suggest that COVID-19 vaccination during pregnancy was not associated with an increased risk of adverse outcomes. Ongoing surveillance of the safety of maternal COVID-19 vaccination is essential as doses continue to be recommended for this group.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.006 | 0.009 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".