Table 3.
Rate ratios of infantile hypertrophic pyloric stenosis (IHPS) by maternal and infant use of penicillin V or amoxicillin during pregnancy and up to 120 days after birth in a cohort of 999 378 singletons, 1996 to 2011
| Use of penicillin V or amoxicillin | No of IHPS cases | Person years | Rate ratio (95% CI)*† |
|---|---|---|---|
| Maternal use during pregnancy: | |||
| 0-27 weeks | 89 | 34 222 | 1.04 (0.83 to 1.29) |
| 28 weeks to birth | 40 | 16 655 | 0.95 (0.69 to 1.31) |
| None | 745 | 273 644 | 1 (reference) |
| Maternal use after birth: | |||
| 0-13 days | 30 | 8163 | 1.35 (0.94 to 1.95)‡ |
| 14-120 days | 25 | 14 229 | 1.11 (0.74 to 1.66) |
| None | 794 | 290 527 | 1 (reference) |
| Use in infants after birth: | |||
| 0-13 days | 0 | 132 | — |
| 14-120 days | 3 | 2808 | 1.20 (0.39 to 3.76) |
| None | 846 | 309 979 | 1 (reference) |
*Adjusted for confounders chosen a priori according to exposure window as described in the methods section (statistical analyses part).
†Estimates not notably changed by performing analyses without adjustment for macrolide use or by adjusting for penicillin V, amoxicillin, or macrolide use, including also use after index exposure (data not shown).
‡Performing this analysis with censoring at infant use of either macrolide, penicillin V, or amoxicillin yielded rate ratio of 1.41 (95% confidence interval 0.98 to 2.03) for days 0 to 13 and 1.11 (0.74 to 1.29) for days 14 to 120.