CI, confidence interval

All associations were adjusted for the confounding effects of year of birth, maternal age, maternal education, race/ethnicity, smoking, single marital status, and pre-pregnancy body-mass index

All 95% confidence interval estimates were based on 2000 bootstrap samples

* The 4-way decomposition analyses stratified by gestational age ranges were similar at 21-27, 28-31, and 32-33 weeks so we grouped these gestational age ranges together