TABLE 3.
Subgroup analyses of effect of vaginal progesterone on preterm birth <37 and 34 weeks of gestation
| Preterm birth <37 weeks of gestation |
Preterm birth <34 weeks of gestation |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Subgroup | No. of trials | Vaginal progesterone | Placebo/no treatment | Relative risk (95% CI) | I2, % | Interaction P value | No. of trials | Vaginal progesterone | Placebo/no treatment | Relative risk (95% CI) | I2, % | Interaction P value |
| Study sample size, n | <0.00001 | 0.0001 | ||||||||||
| <150 | 772,74–78,81 | 59/342 (17.3%) | 136/336 (40.5%) | 0.43 (0.33–0.55) | 0 | 6160,161,162,163 | 13/297 (4.4%) | 52/291 (17.9%) | 0.27 (0.15–0.49) | 0 | ||
| ≥150 | 373,79,80 | 421/1156 (36.4%) | 423/1142 (37.0%) | 0.98 (0.88–1.09) | 0 | 3162–164 | 183/1156 (15.8%) | 192/1142 (16.8%) | 0.94 (0.78–1.13) | 0 | ||
| Study setting | <0.00001 | 0.0003 | ||||||||||
| Low/middle-income countries | 772,74–78,81 | 59/342 (17.3%) | 136/336 (40.5%) | 0.43 (0.33–0.55) | 0 | 6162 | 13/297 (4.4%) | 52/291 (17.9%) | 0.27 (0.15–0.49) | 0 | ||
| High-income countries | 279,80 | 286/847 (33.8%) | 291/840 (34.6%) | 0.97 (0.85–1.11) | 0 | 2162 | 134/847 (15.8%) | 138/840 (16.4%) | 0.96 (0.77–1.20) | 0 | ||
| Both low/middle- and high-income countries | 173 | 135/309 (43.7%) | 132/302 (43.7%) | 1.00 (0.83–1.20) | NA | 1162 | 49/309 (15.9%) | 54/302 (17.9%) | 0.89 (0.62–1.26) | NA | ||
| Study center status | <0.00001 | 0.0003 | ||||||||||
| Single center | 772,74–78,81 | 59/342 (17.3%) | 136/336 (40.5%) | 0.43 (0.33–0.55) | 0 | 6160,161,162,163 | 13/297 (4.4%) | 52/291 (17.9%) | 0.27 (0.15–0.49) | 0 | ||
| Multicenter | 373,79,80 | 421/1156 (36.4%) | 423/1142 (37.0%) | 0.98 (0.88–1.09) | 0 | <0.0001 | 3162–164 | 183/1156 (15.8%) | 192/1142 (16.8%) | 0.94 (0.78–1.13) | 0 | |
| Trial registration status | 0.0001 | 0.0002 | ||||||||||
| Registered | 573,77–80 | 437/1225 (35.7%) | 456/1207 (37.8%) | 0.88 (0.72–1.07) | 62 | 5162 | 188/1225 (15.3%) | 203/1207 (16.8%) | 0.90 (0.74–1.11) | 15 | ||
| Not registered | 572,74–76,81 | 43/273 (15.8%) | 103/271 (38.0%) | 0.42 (0.31–0.57) | 0 | 4162 | 8/228 (3.5%) | 41/226 (18.1%) | 0.21 (0.10–0.44) | 0 | ||
| Mean gestational age at treatment initiation, weeks | 0.01 | <0.0001 | ||||||||||
| <24 | 673,74,78–81 | 447/1279 (35.0%) | 485/1262 (38.4%) | 0.76 (0.60–0.98) | 75 | 5162 | 190/1234 (15.4%) | 206/1217 (16.9%) | 0.91 (0.76–1.09) | 0 | ||
| ≥24 | 472,75–77 | 33/219 (15.1%) | 74/216 (34.3%) | 0.44 (0.31–0.63) | 0 | 4162 | 6/219 (2.7%) | 38/216 (17.6%) | 0.16 (0.07–0.36) | 0 | ||
| Daily dose of vaginal progesterone, mg | 0.97 | 0.54 | ||||||||||
| 90–100 | 772,73–77,80 | 308/968 (31.8%) | 363/953 (38.1%) | 0.62 (0.45–0.85) | 75 | 7162 | 121/968 (12.5%) | 157/953 (16.5%) | 0.51 (0.28–0.92) | 72 | ||
| ≥200 | 378,79,81 | 172/530 (32.5%) | 196/525 (37.3%) | 0.61 (0.32–1.14) | 84 | 2162 | 75/485 (15.5%) | 87/480 (18.1%) | 0.69 (0.32–1.47) | 64 | ||
Data are n/N.
CI, confidence interval; NA, not applicable.