Table 3. Association between antibiotic exposure and risk of ASD in the sibling cohort.
| Variable | Person-years | Number of events | HR [95% CI] | |
|---|---|---|---|---|
| Unadjusted | Adjusted a | |||
| Main analysis | ||||
| Prenatal antibiotics exposure | 700 610 | 977 | 1.05 [0.90 ,1.22] | 1.08 [0.90 , 1.30] |
| Stratified by sex: | ||||
| Male | 357 076 | 786 | 1.21 [0.97 , 1.52] | 1.14 [0.89 , 1.47] |
| Female | 343 535 | 191 | 1.03 [0.64 , 1.64] | 1.10 [0.57 , 2.11] |
| Stratified by region: | ||||
| Rural | 361 486 | 378 | 1.12 [0.87 , 1.45] | 1.19 [0.85 , 1.67] |
| Urban | 339 124 | 599 | 1.07 [0.88 , 1.30] | 1.07 [0.84 , 1.37] |
| Exposure by trimester: b | ||||
| None | 368 871 | 501 | 1.00 [Reference] | 1.00 [Reference] |
| First | 141 496 | 190 | 1.15 [0.94 , 1.41] | 1.25 [1.00 , 1.58] |
| Second | 159 418 | 249 | 1.13 [0.94 , 1.36] | 1.16 [0.94 , 1.44] |
| Third | 143 039 | 207 | 1.21 [0.99 , 1.47] | 1.25 [1.00 , 1.57] |
| Secondary analyses | ||||
| Antibiotic class | ||||
| None | 368 871 | 501 | 1.00 [Reference] | 1.00 [Reference] |
| Penicillin | 219 436 | 327 | 1.11 [0.94 , 1.32] | 1.18 [0.97 , 1.45] |
| Macrolides and related antibiotics | 59 611 | 93 | 1.27 [0.96 , 1.68] | 1.24 [0.91 , 1.68] |
| Other Beta lactams | 57 224 | 82 | 1.27 [0.95 , 1.71] | 1.29 [0.94 , 1.77] |
| Others | 80 109 | 101 | 0.96 [0.74 , 1.26] | 1.01 [0.75 , 1.36] |
| Number of antibiotic courses | ||||
| 0 | 368 871 | 501 | 1.00 [Reference] | 1.00 [Reference] |
| 1 | 226 323 | 311 | 0.99 [0.83 , 1.18] | 1.04 [0.85 , 1.28] |
| 2 | 70 245 | 115 | 1.14 [0.86 , 1.51] | 1.17 [0.84 , 1.62] |
| > = 3 | 35 171 | 50 | 1.33 [0.87 , 2.03] | 1.20 [0.73 , 1.96] |
| Cumulative antibiotic duration [days] | ||||
| 0 | 368 871 | 501 | 1.00 [Reference] | 1.00 [Reference] |
| 1–7 | 148 816 | 200 | 0.97 [0.78 , 1.19] | 1.04 [0.81 , 1.32] |
| 8–14 | 111 409 | 165 | 1.03 [0.82 , 1.30] | 1.06 [0.81 , 1.38] |
| >14 | 71 514 | 111 | 1.29 [0.96 , 1.72] | 1.26 [0.89 , 1.79] |
a Adjusted for sex, region, SES, maternal age at delivery, prenatal infections, prenatal antidepressants use, size for gestational age, childhood medical conditions [epilepsy, infections, neonatal jaundice, asthma and a diagnosis with other developmental disability disorder], antibiotics use in the first year of life, birth complications, mode of delivery, multiple birth, breastfeeding initiation, year of birth, season of birth, and birth order.
b First trimester = 0 to 13 weeks of pregnancy, second = 13 to 27 weeks, third = 28 weeks until date of birth