Maternal antibiotic use and child asthma according to potential confounders in Manitoba, Canada, 1996–2012
| Dyads | Maternal antibiotic use during pregnancy | Childhood asthma | ||
| Cases | Incidence rate (95% CI) per 1000 person-years | |||
| All dyads | 213 661 | 78 522 (36.8) | 21 483 | 10.2 (10.0–10.3) |
| Maternal antibiotic use during pregnancy | ||||
| Yes | 78 522 | na | 9091 | 11.9 (11.6–12.1) |
| No | 135 139 | na | 12 392 | 9.2 (9.0–9.4) |
| Infant antibiotic use before age 12 months | ||||
| Yes | 96 525 | 42 188 (43.7) | 11 774 | 11.7 (11.4–11.9) |
| No | 117 136 | 36 334 (31.0) | 9709 | 8.8 (8.6–9.0) |
| Infant sex | ||||
| Male | 109 437 | 40 267 (36.8) | 12 615 | 11.8 (11.6–12.0) |
| Female | 104 224 | 38 255 (36.7) | 8868 | 8.5 (8.3–8.6) |
| Residence location# | ||||
| Urban | 115 604 | 40 246 (34.8) | 13 984 | 12.4 (12.2–12.6) |
| Rural | 97 549 | 38 056 (39.0) | 7458 | 7.6 (7.4–7.7) |
| Gestational age weeks | ||||
| <35 | 5016 | 1962 (39.1) | 761 | 16.3 (15.2–17.5) |
| 35–<37 | 9192 | 3594 (39.1) | 1136 | 13.2 (12.4–14.0) |
| 37–<39 | 43 799 | 16 429 (37.5) | 4466 | 10.6 (10.3–11.0) |
| ≥39 | 155 654 | 56 537 (36.3) | 15 120 | 9.7 (9.5–9.8) |
| Children in household# | ||||
| 1 | 80 939 | 28 053 (34.7) | 9273 | 11.7 (11.5–11.9) |
| 2 | 71 403 | 26 138 (36.6) | 7363 | 10.3 (10.1–10.6) |
| 3 | 34 234 | 13 515 (39.5) | 3040 | 8.9 (8.5–9.2) |
| ≥4 | 26 842 | 10 698 (39.9) | 1777 | 6.7 (6.4–7.1) |
| Maternal asthma | ||||
| Yes | 12 780 | 7180 (56.2) | 2264 | 21.0 (20.1–21.9) |
| No | 200 881 | 71 342 (35.5) | 19 219 | 9.6 (9.4–9.7) |
| Neighbourhood income quintile# | ||||
| Q1 (lowest) | 56 019 | 23 426 (41.8) | 5832 | 10.6 (10.4–10.9) |
| Q2 | 44 214 | 16 637 (37.6) | 4340 | 9.8 (9.5–10.1) |
| Q3 | 39 797 | 14 499 (36.4) | 4000 | 10.1 (9.8–10.4) |
| Q4 | 39 017 | 12 962 (33.2) | 3835 | 10.0 (9.6–10.2) |
| Q5 (highest) | 34 106 | 10 778 (31.6) | 3435 | 10.1 (9.8–10.5) |
| Maternal age years | ||||
| <20 | 20 308 | 9083 (44.7) | 2010 | 9.8 (9.4–10.2) |
| 20–24 | 46 589 | 19 700 (42.3) | 4557 | 9.8 (9.5–10.1) |
| 25–29 | 63 685 | 22 758 (35.7) | 6359 | 10.1 (9.8–10.3) |
| 30–34 | 55 474 | 18 160 (32.7) | 5751 | 10.5 (10.3–10.8) |
| ≥35 | 27 605 | 8821 (32.0) | 2806 | 10.5 (10.1–10.9) |
| Delivery method | ||||
| Caesarean section | 41 248 | 15 557 (37.7) | 4614 | 11.8 (11.5–12.2) |
| Vaginal | 172 413 | 62 965 (36.5) | 16 869 | 9.8 (9.6–9.9) |
| Birth weight g | ||||
| <3000 | 36 833 | 13 640 (37.0) | 4322 | 12.0 (11.6–12.4) |
| 3000–<3500 | 70 519 | 23 353 (36.0) | 7013 | 10.1 (9.8–10.3) |
| 3500–<4500 | 99 149 | 36 626 (36.9) | 9492 | 9.6 (9.4–9.8) |
| ≥4500 | 6571 | 2613 (39.8) | 656 | 10.1 (9.3–10.9) |
| Feeding method at birth | ||||
| Exclusively breastfed | 108 147 | 36 856 (34.1) | 11 127 | 9.9 (9.7–10.1) |
| Partially breastfed | 60 891 | 22 686 (37.3) | 5697 | 10.5 (10.2–10.8) |
| Formula-fed | 41 026 | 17 470 (42.6) | 4288 | 10.5 (10.1–10.8) |
Data are presented as n or n (%), unless otherwise stated. n=213 661. na: not applicable. #: excluding dyads with missing data, as reported in table 1.