Maternal age, gestation at baseline, residential municipality at baseline, family income, maternal and parental education, maternal and parental history of asthma, atopic eczema and allergic rhinitis, changes in maternal diet in the previous one month, season at baseline, maternal smoking during pregnancy, baby’s older siblings, baby’s sex, baby’s birth weight, household smoking in the same room as infant, breastfeeding duration, and age of infant at third survey