Table 3. Results Summary for Spontaneous Abortion, Congenital Defects, Stillbirth, and Preterm Birth With Smallpox Vaccination in Pregnancy.
| Outcome | No. of Studies | Control (n/N) | Control (%)* | Vaccinated (n/N) | Vaccinated (%)* | Measure of Effect* | Effect Size (95% CI) | Heterogeneity (%) |
|---|---|---|---|---|---|---|---|---|
| Primary | ||||||||
| Spontaneous abortion | ||||||||
| First trimester | 3 | 136/3,495 | 5.5 | 44/770 | 5.7 | Pooled RR (random) | 1.62 (0.43–6.19) | I2 = 92.9 |
| All trimesters | 8 | 457/7,560 | 6.7 | 246/4,640 | 7.7 | Pooled RR (random) | 1.03 (0.76–1.41) | I2=62.5 |
| Congenital defect | ||||||||
| First trimester | 5 | 917/28,879 | 1.5 | 80/5,274 | 2.4 | Pooled RR (random) | 1.34 (1.02–1.77) | I2=0.0 |
| All trimesters | 8 | 946/30,804 | 1.6 | 153/8,781 | 2.1 | Pooled RR (random) | 1.25 (0.99–1.56) | I2=0.0 |
| Secondary | ||||||||
| Stillbirth | ||||||||
| All trimesters | 7 | 121/5,974 | 2.4 | 126/5,009 | 2.4 | Pooled RR (random) | 1.03 (0.75–1.4) | I2=10.6 |
| Preterm birth | ||||||||
| All trimesters | 6 | 2,205/29,370 | 10.0 | 638/7,953 | 8.0 | Pooled RR (random) | 0.84 (0.62–1.15) | I2=85.6 |
CI, confidence interval; RR, relative risk.
*
The percentages are pooled from the individual studies using random-effects models.15