Covariates
Covariates adjusted for in models included infant characteristics, such as sex, gestational age at birth and season of birth, and maternal characteristics including age, education, height, BMI, gravidity, vitamin D treatment group, daily protein intake (kg), urinary cotinine levels, maternal smoking and tobacco use during pregnancy, C-reactive protein concentrations at delivery and household asset index.Gestational age was estimated at the time of enrolment using a combination of the last menstrual period and ultrasound. Smoking status was described using urinary cotinine levels, where women with cotinine ≤ 50 ng/ml were classified as non-smokers and women with levels > 50 ng/ml were classified as smokers