Background: The relations of birth weight and maternal body mass index (BMI) to overweight remain unresolved. We prospectively examined the relations of birth weight with various anthropometric measures at age 3 to 6 years, the effect of maternal BMI, and the patterns of these relations in an analysis using 9 birth weight categories.
Methods: The subjects were 210 172 singleton infants born alive with a gestational age ≥ 28 weeks between October 1993 and December 1996; the subjects were followed up in 2000. Birth weight, maternal height and weight, and other relevant information were measured or collected prospectively. Overweight and underweight were defined by using National Center for Health Statistics/World Health Organization reference data. Logistic regression models were used to estimate relative risks. Analyses stratified by quartile of maternal BMI were performed to examine the effects of maternal BMI on the associations of birth weight with overweight and underweight.
Results: Birth weight was linearly associated with height, weight, and BMI at age 3-6 years. Adjustment for maternal BMI did not alter this association. Birth weight was positively associated with overweight and negatively associated with underweight. The relation curves for both overweight and underweight resembled half of a flat parabolic curve. The associations for overweight and underweight were slightly stronger for the highest and lowest quartiles of maternal BMI, respectively.
Conclusions: Higher birth weight is associated with an increased risk for childhood overweight, and lower birth weight with an increased risk for underweight. The associations between birth weight and early childhood anthropometric growth measures could not explained by maternal BMI.