Birth size, infant growth, and child BMI at age 5 years in a multiethnic population

Abstract

Child overweight is a public health concern and it is imperative that steps are taken to examine early factors that may contribute to this unhealthful start to life. Prenatal and postnatal determinants of overweight (e.g., maternal overweight, birth weight, and increased weight gain during infancy) have been studied. However, few studies have examined the effect of other measures of birth size (birth length, indices of weight/length, gestational age) and infant growth patterns on BMI at age five years in a multiethnic population. This is a retrospective, longitudinal study using data from the Kaiser Permanente Hawaiʻi Electronic Medical Record. Singleton children, born in years 2004 and 2005 at Kaiser Permanente, with birth and linked maternal information were initially included (n = 894). Subsequently, children with measured weights (n = 597) and lengths (n = 473) from ages 2 to 4 and 22 to 24 months were included. A higher birth weight was associated with a higher BMI at age five years after controlling for gestational age, age, sex, race/ethnicity, and maternal factors (prepregnancy weight, age, education, and smoking). Birth length was not associated with BMI at age five after adjusting for birth weight and gestational age. A higher prepregnancy maternal weight was also associated with a higher child BMI at age five years. For every 100 g/month increase in weight and 1 cm increase in length over the infant period of 20 months, BMI increased by 1 kg/m2 at age five years. However, this was not true for change in BMI during infancy. The effect of birth weight on BMI at age five years was not mediated by infant growth and the interaction was not significant. Birth weight, change in infant weight, and BMI at age five varied by race/ethnicity, but not by sex. Birth weight and change in infant weight was higher in Whites and Other Pacific Islanders, with most differences observed after age two years. Early indicators such as a higher birth weight and change in infant weight and length, and higher maternal pre-pregnancy weight, are key indicators associated with a higher child BMI at age five.