Table 2.
Odds ratios for the association between COVID-19 vaccination and miscarriage from multinomial logistic regression models
| Number of pregnancies | Number (%) of ongoing pregnancies | Number (%) of miscarriages | Odds ratio (95% CI)a | p-value | Adjusted odds ratio (95% CI)b | p-value | |
|---|---|---|---|---|---|---|---|
| Primary analysis (historical controls) | |||||||
| Unvaccinated | 56,340 | 44,669 (79.3%) | 5566 (9.9%) | 1 | 1 | ||
| Vaccinated | 18,780 | 14,119 (75.2%) | 1716 (9.1%) | 0.98 (0.93–1.04) | 0.55 | 1.02 (0.96–1.09) | 0.49 |
| BNT162b2 subgroup analysis (historical controls) | |||||||
| Unvaccinated | 41,025 | 32,958 (80.3%) | 3804 (9.3%) | 1 | 1 | ||
| Vaccinated | 13,675 | 10,485 (76.7%) | 1147 (8.4%) | 0.96 (0.89–1.03) | 0.22 | 1.00 (0.93–1.08) | 0.90 |
| mRNA-1273 subgroup analysis (historical controls) | |||||||
| Unvaccinated | 6780 | 5646 (83.3%) | 511 (7.5%) | 1 | 1 | ||
| Vaccinated | 2260 | 1744 (77.2%) | 162 (7.2%) | 1.06 (0.88–1.29) | 0.52 | 1.07 (0.87–1.33) | 0.51 |
| ChAdOx1-S/nCoV-19 subgroup analysis (historical controls) | |||||||
| Unvaccinated | 7836 | 5564 (71.0%) | 1152 (14.7%) | 1 | 1 | ||
| Vaccinated | 2612 | 1659 (63.5%) | 406 (15.5%) | 1.17 (1.03–1.33) | 0.01 | 1.17 (1.03–1.34) | 0.02 |
| Supplementary analysis (contemporary controls) | |||||||
| Unvaccinated | 18,780 | 14,162 (75.4%) | 1878 (10.0%) | 1 | 1 | ||
| Vaccinated | 18,780 | 14,119 (75.2%) | 1716 (9.1%) | 0.91 (0.85–0.98) | 0.01 | 0.96 (0.88–1.04) | 0.35 |
| BNT162b2 subgroup analysis (contemporary controls) | |||||||
| Unvaccinated | 13,675 | 10,494 (76.7%) | 1258 (9.2%) | 1 | 1 | ||
| Vaccinated | 13,675 | 10,485 (76.7%) | 1147 (8.4%) | 0.91 (0.83–0.99) | 0.03 | 0.99 (0.89–1.09) | 0.81 |
| mRNA-1273 subgroup analysis (contemporary controls) | |||||||
| Unvaccinated | 2260 | 1794 (79.4%) | 198 (8.8%) | 1 | 1 | ||
| Vaccinated | 2260 | 1744 (77.2%) | 162 (7.2%) | 0.85 (0.68–1.07) | 0.17 | 1.04 (0.76–1.43) | 0.79 |
| ChAdOx1-S/nCoV-19 subgroup analysis (contemporary controls) | |||||||
| Unvaccinated | 2612 | 1731 (66.3%) | 389 (14.9%) | 1 | 1 | ||
| Vaccinated | 2612 | 1659 (63.5%) | 406 (15.5%) | 1.08 (0.92–1.27) | 0.32 | 0.92 (0.76–1.11) | 0.41 |
All analyses exclude women with confirmed SARS-CoV-2 infection between 6 weeks preconception and the earliest of either: end of pregnancy or the end of the exposure period at 19 + 6 weeks gestation.
CI confidence interval.
aAdjusting for matching factors: maternal age and gestational age at the date of vaccination of index vaccinated pregnancy (and season of conception for primary and primary subgroup analysis).
bAdditionally adjusting for deprivation, urban/rural status, and clinical vulnerability (and ethnicity and season of conception in Supplementary analyses).