Variable | No. of events | Person-years* | Type of analysis; HR (95% CI) | |
---|---|---|---|---|
Unadjusted | Adjusted† | |||
Main analysis | ||||
Prenatal antibiotic exposure | ||||
Unexposed | 2913 | 360 947 | 1.00 (Ref.) | 1.00 (Ref.) |
Exposed | 3112 | 326 402 | 1.07 (1.01–1.14) | 1.06 (0.99–1.13) |
Secondary analyses | ||||
Exposure by trimester‡§ | ||||
None | 2913 | 360 947 | 1.00 (Ref.) | 1.00 (Ref.) |
First | 1446 | 138 371 | 1.02 (0.94–1.11) | 1.03 (0.94–1.13) |
Second | 1506 | 145 603 | 1.13 (1.04–1.23) | 1.10 (1.00–1.20) |
Third | 1258 | 131 952 | 1.02 (0.93–1.11) | 1.02 (0.93–1.12) |
Antibiotic class§ | ||||
None | 2913 | 360 947 | 1.00 (Ref.) | 1.00 (Ref.) |
Penicillin | 2063 | 215 600 | 1.01 (0.94–1.09) | 1.03 (0.95–1.11) |
Non-penicillin β-lactams | 582 | 55 855 | 1.18 (1.04–1.34) | 1.09 (0.96–1.25) |
Macrolides and related antibiotics | 700 | 55 595 | 1.12 (0.99–1.26) | 1.07 (0.95–1.21) |
Other | 784 | 77 095 | 1.01 (0.90–1.13) | 1.01 (0.89–1.13) |
No. of antibiotic courses | ||||
0 | 2913 | 360 947 | 1.00 (Ref.) | 1.00 (Ref.) |
1 | 1921 | 223 769 | 1.05 (0.98–1.13) | 1.04 (0.96–1.12) |
2 | 750 | 68 775 | 1.10 (0.98–1.28) | 1.11 (0.99–1.25) |
≥ 3 | 441 | 33 859 | 1.12 (0.97–1.30) | 1.10 (0.95–1.28) |
Cumulative antibiotic duration, d | ||||
0 | 2913 | 360 947 | 1.00 (Ref.) | 1.00 (Ref.) |
1–7 | 1233 | 146 636 | 1.06 (0.97–1.16) | 1.04 (0.95–1.15) |
8–14 | 1039 | 110 020 | 1.04 (0.94–1.14) | 1.03 (0.94–1.14) |
> 14 | 840 | 69 746 | 1.14 (1.02–1.28) | 1.13 (1.01–1.27) |
Note: CI = confidence interval, HR = hazard ratio, Ref. = reference.
↵* Values for person-years were rounded to the nearest integer.
↵† Adjusted for sex, mother’s age at delivery, birth order, year of birth and prenatal exposure to antidepressants.
↵‡ First trimester = 0–13 weeks of pregnancy, second trimester = 14–27 weeks, third trimester = 28 weeks until date of birth.
↵§ A child could be exposed to antibiotics during multiple trimesters and could be exposed to multiple antibiotic classes.