Associations between maternal prepregnancy body mass index and child neurodevelopment at 2 years of age

OBJECTIVE: Both underweight and obese mothers have an increased risk for adverse offspring outcomes. Few studies have examined the association between prepregnancy body mass index (BMI) and children's neurodevelopment. SUBJECTS: We used data from the nationally representative Early Childhood Longitudinal Study-Birth Cohort (ECLS-B; n = 6850). Children were classified according to their mother's prepregnancy BMI (kg m(-2)) status: underweight (BMI <18.5), normal weight (BMI 18.5-24.9), overweight (BMI 25.0-29.9), obese class I (BMI 30.0-34.9), and obese class II and III (BMI >= 35.0). Children's age-adjusted mental development index (MDI) and psychomotor development index (PDI) T-scores (mean 50, s.d. 10) were obtained using a validated shortened version of the Bayley Scales of Infant Development-II at approximately 2 years of age. While adjusting for sociodemographics, we estimated the average MDI and PDI scores or the risk of delayed (< -1 s.d. vs >1 s.d.) mental or motor development, relative to children of normal weight mothers. RESULTS: Compared with children of normal weight mothers, MDI scores were lower among children of mothers of all other prepregnancy BMI categories, with the greatest adjusted difference among children of class II and III obese mothers (-2.13 (95% CI -3.32, -0.93)). The adjusted risk of delayed mental development was increased among children of underweight (risk ratio (RR) 1.36 (95% CI 1.04, 1.78)) and class II and III obese (RR 1.38 (95% CI 1.03, 1.84)) mothers. Children's PDI scores or motor delay did not differ by maternal prepregnancy BMI. CONCLUSION: In this nationally representative sample of 2-year-old US children, low and very-high maternal prepregnancy BMI were associated with increased risk of delayed mental development but not motor development.