<scp>COVID</scp>‐19 vaccination around the time of conception and risk of placenta‐mediated adverse pregnancy outcomes
Bibliographic record
Abstract
INTRODUCTION: Although numerous studies have documented no association between COVID-19 vaccination during pregnancy and maternal and fetal health outcomes, fewer studies have evaluated fetal health effects after COVID-19 vaccination around the time of conception and early pregnancy, a time when maternal exposures may affect early placentation and the subsequent risk of placenta-mediated adverse pregnancy outcomes. MATERIAL AND METHODS: We used province-wide databases in Ontario to conduct a population-based cohort study including all live and stillbirths ≥20 weeks' gestation with a last menstrual period (LMP) between April 1 and December 31, 2021. We deterministically linked birth registry data to the vaccine registry for all 80 253 eligible pregnancies; 31 209 (38.9%) received ≥1 dose of the COVID-19 vaccine around the time of conception or first trimester. Using Cox regression, we estimated propensity score weighted hazard ratios (aHR) and 95% confidence intervals (CI) for associations between ≥1 dose of mRNA COVID-19 vaccine during the periconceptional/first trimester exposure window (28 days before the LMP to the end of first trimester) and study outcomes: hypertensive disorders (gestational hypertension, preeclampsia, eclampsia), placental abruption, preterm birth (<37 weeks), small-for-gestational-age (SGA) birth (<10th percentile), and stillbirth. RESULTS: COVID-19 vaccination around the time of conception or first trimester was associated with a small increased risk of hypertensive disorders in pregnancy in exposed versus unexposed individuals (7.4% vs. 6.1%; aHR: 1.10, 95% CI: 1.03-1.17), mostly attributed to gestational hypertension (5.0% vs. 4.1%; aHR 1.13, 95% CI: 1.05-1.22). There was no increased risk of preeclampsia (1.8% vs. 1.5%; aHR 1.08, 95% CI: 0.95-1.22), eclampsia (0.1% vs. 0.1%; aHR: 1.12, 95% CI 0.65-1.95), placental abruption (0.8% vs. 1.0%; aHR: 0.77, 95%CI: 0.65-0.91), preterm birth (8.0% vs. 8.9%; aHR: 0.92, 95%CI: 0.87-0.97), SGA birth (8.9% vs. 9.3%; aHR: 1.00, 95%CI: 0.95-1.06), or stillbirth (0.4% vs. 0.6%; aHR: 0.66, 95%CI: 0.52-0.82). CONCLUSIONS: This population-based Canadian study provides additional evidence evaluating COVID-19 vaccine administration around the start of pregnancy. While we identified no association with most placenta-mediated outcomes, we report a slight increase in the rate of gestational hypertension. This could be a true association or attributed to residual confounding. Further research is needed to verify.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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 source (direct Gemma or distilled Codex), 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".