| Wheeze, 6–18 months, | LRTI, 0–18 months, | LRTI hospitalised, 0–18 months, | |||||||
| n = 12 656 | n = 5089 | n = 1319 | |||||||
| % | cRR | aRR (95% CI) | % | cRR | aRR (95% CI) | % | cRR | aRR (95% CI) | |
| Folic acid in first trimester | |||||||||
| No | 38.8% | 1.00 | 1.00 (–) | 16.4% | 1.00 | 1.00 (–) | 4.1% | 1.00 | 1.00 (–) |
| Yes | 41.1% | 1.06 | 1.06 (1.03 to 1.10) | 17.0% | 1.04 | 1.09 (1.02 to 1.15) | 4.5% | 1.09 | 1.24 (1.09 to 1.41) |
| Folic acid after first trimester | |||||||||
| No | 39.7% | 1.00 | 1.00 (–) | 17.0% | 1.00 | 1.00 (–) | 4.6% | 1.00 | 1.00 (–) |
| Yes | 40.8% | 1.03 | 1.00 (0.97 to 1.03) | 16.6% | 0.98 | 0.98 (0.92 to 1.04) | 4.1% | 0.89 | 0.86 (0.75 to 0.97) |
*Exposures in first and after first trimester adjusted for each other, and in addition adjusted for other vitamin supplements and cod liver oil in pregnancy, vitamin supplements and cod liver oil at 6 months of age, and for maternal age, maternal atopy, maternal smoking in pregnancy, maternal educational level, postnatal parental smoking, sex, parity, birth weight, season born, breast feeding and type of day care.
aRR, adjusted relative risk; cRR, crude relative risk; LRTI, lower respiratory tract infection.