Table 3 Incidence proportions (%), crude relative risks and adjusted* relative risks with 95% CI, for wheeze, lower respiratory tract infections (LRTIs) and hospitalisations for LRTIs according to prenatal exposure to folic acid supplements for children born in 2000–2005
Wheeze, 6–18 months,LRTI, 0–18 months,LRTI hospitalised, 0–18 months,
n = 12 656n = 5089n = 1319
%cRRaRR (95% CI)%cRRaRR (95% CI)%cRRaRR (95% CI)
Folic acid in first trimester
    No38.8%1.001.00 (–)16.4%1.001.00 (–)4.1%1.001.00 (–)
    Yes41.1%1.061.06 (1.03 to 1.10)17.0%1.041.09 (1.02 to 1.15)4.5%1.091.24 (1.09 to 1.41)
Folic acid after first trimester
    No39.7%1.001.00 (–)17.0%1.001.00 (–)4.6%1.001.00 (–)
    Yes40.8%1.031.00 (0.97 to 1.03)16.6%0.980.98 (0.92 to 1.04)4.1%0.890.86 (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.