Table 3.
Risk ratio of preterm delivery by antibiotic initiation between 24 and 37 weeks’ gestation, The Tsepamo Study
| Antibiotic Initiation | Initiation | Number of individuals | Events, number | Unadjusted Risk Ratio (95% CI) for initiation versus no initiation | Adjusteda Risk ratio (95% CI) for initiation versus no initiation |
|---|---|---|---|---|---|
|
Antibiotic initiation at:
|
|||||
| 24 weeks | No | 110,032 | 15,672 | ||
| Yes | 1,371 | 219 | 1.12 (0.99, 1.27) | 1.09 (0.97, 1.23) | |
| 25 weeks | No | 108,459 | 15,233 | ||
| Yes | 1,382 | 248 | 1.28 (1.14, 1.43) | 1.24 (1.11, 1.39) | |
| 26 weeks | No | 106,917 | 14,802 | ||
| Yes | 1,310 | 199 | 1.10 (0.96, 1.25) | 1.09 (0.96, 1.24) | |
| 27 weeks | No | 105,239 | 14,306 | ||
| Yes | 1,400 | 218 | 1.15 (1.01, 1.30) | 1.13 (1.00, 1.27) | |
| 28 weeks | No | 103,623 | 13,808 | ||
| Yes | 1,326 | 208 | 1.18 (1.04, 1.33) | 1.15 (1.02, 1.30) | |
| 29 weeks | No | 101,839 | 13,208 | ||
| Yes | 1,403 | 219 | 1.20 (1.06, 1.36) | 1.17 (1.04, 1.32) | |
| 30 weeks | No | 100,090 | 12,617 | ||
| Yes | 1,363 | 205 | 1.19 (1.05, 1.36) | 1.16 (1.03, 1.32) | |
| 31 weeks | No | 98,143 | 11,869 | ||
| Yes | 1,376 | 177 | 1.06 (0.93, 1.22) | 1.04 (0.90, 1.19) | |
| 32 weeks | No | 96,226 | 11,031 | ||
| Yes | 1,256 | 177 | 1.23 (1.07, 1.41) | 1.19 (1.04, 1.36) | |
| 33 weeks | No | 94,100 | 9,990 | ||
| Yes | 1,231 | 146 | 1.12 (0.96 1.30) | 1.10 (0.95, 1.29) | |
| 34 weeks | No | 91,797 | 8,769 | ||
| Yes | 1,227 | 145 | 1.24 (1.06, 1.44) | 1.22 (1.05, 1.42) | |
| 35 weeks | No | 88,846 | 6,923 | ||
| Yes | 1,208 | 103 | 1.09 (0.91, 1.32) | 1.07 (0.89, 1.29) | |
| 36 weeks | No | 85,324 | 4,551 | ||
| Yes | 1,156 | 6 | 0.10 (0.04, 0.22) | -- | |
| Pooled (24-36 weeks)b | No | 1,290,635 | 152,779 | ||
| Yes | 17,009 | 2,270 | 1.13 (1.09, 1.17) | 1.11 (1.06, 1.15) | |
|
Susceptible to immortal time bias:
|
|||||
| Antibiotic initiation at 24-37 weeks’ gestation | No | 94,394 | 13,621 | ||
| Yes | 17,009 | 2,270 | 0.92 (0.89, 0.96) | 0.90 (0.86, 0.94) | |
Adjusted for maternal age (<18 years; 18-35 years; >=35 years), education (secondary or higher; none or primary or unknown), occupation (salaried; non-salaried), parity (1 or more children; 0 children or missing), marital status (married; single, widowed, divorced or missing), HIV status (yes; no or unknown), delivery year (2014-2016; 2017-2019; 2020-2021), trimester of presentation to care (<12 weeks; 12-24 weeks), delivery site (Gaborone or Francistown; all others), prior preterm delivery or stillbirth (yes; no; unknown), and syphilis diagnosis at presentation to care (yes; no; unknown)
The adjusted pooled model additionally includes ‘trial’ as an adjustment variable. 95% CIs for the pooled models were obtained via bootstrapping