Table 2 Incidence proportions (%) and adjusted* relative risks with 95% CI for wheeze, lower respiratory tract infections (LRTIs) and hospitalisations for LRTIs up to 18 months of age according to prenatal exposure to folic acid supplements for children born in 2000–2005

Folic acid supplements in pregnancy		Wheeze, 6–18 months			LRTI, 0–18 months		LRTI hospitalised, 0–18 months
Before week 12	After week 12	n	%	aRR (95% CI)	%	aRR (95%CI)	%	aRR (95%CI)
No	No	6835	38.2	1.00	16.7%	1.00	4.3%	1.00
No	Yes	4431	39.5	1.01 (0.96 to 1.07)	16.0%	0.97 (0.88 to 1.08)	3.8%	0.92 (0.73 to 1.15)
Yes	No	7145	41.0	1.07 (1.03 to 1.12)	17.3%	1.10 (1.01 to 1.20)	5.0%	1.28 (1.07 to 1.53)
Yes	Yes	13 666	41.2	1.07 (1.02 to 1.12)	16.8%	1.07 (0.98 to 1.16)	4.2%	1.08 (0.90 to 1.29)

*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; LRTI, lower respiratory tract infection.