Pre-pregnancy Obesity in Relation to Preterm Birth and Macrosomia

The prevalence of overweight and obesity is increasing rapidly in the US, especially among Black women of childbearing age. Obesity causes major changes in maternal metabolism and may be involved in increased energy accumulation by the fetus. In studies of predominantly White populations, obesity has been linked to an increased risk of adverse pregnancy outcomes including macrosomia (large-for-gestational age). Studies on preterm birth are inconclusive, with some studies suggesting an increased risk of preterm birth associated with obesity. Rates of preterm birth and macrosomia have been increasing in the US. Moreover, preterm birth is nearly twice as common among Black women as White women. We will assess the relation of pre-pregnancy body mass index (kg/m2) and body fat distribution (waist circumference) with risk of preterm birth (<37 weeks of gestation) and macrosomia (birth weight ≥4000 g) in the Black Women’s Health Study. We will also assess whether gestational weight gain and parity modify these associations. Birth outcome data will be derived from mothers ages 21-44 years reporting a singleton birth during 1995-2003. Preterm birth data have already been validated; infant birth weight will be validated using birth registry data from the Massachusetts Department of Public Health. The proposed study of modifiable anthropometric risk factors for preterm birth and macrosomia offers potential to reduce adverse birth outcomes in US Black women.