Macrosomia: influence of maternal overweight among a low-income population.

Macrosomia (birth weight greater than 4000 gm) is associated with a wide variety of adverse intrapartum and perinatal outcomes. To evaluate the effect of pregravid obesity on infant birth weight, we examined data from a low-income population of women (n = 127,879). The population was divided into five groups on the basis of pregravid body mass index (weight/height) designated by the National Health and Nutrition Examination Survey II reference population (less than 25th percentile, 25th to less than 75th percentile, 75th to less than 85th percentile, 85th to less than 95th percentile, and greater than or equal to 95th percentile). The prevalence of infant macrosomia ranged from 5% for the lowest group to 17% for the highest group. With the use of the second group (25th to less than 75th percentile) as a reference, odds ratios (adjusted for maternal age, smoking status, race, height, parity, gestational age, and infant sex) for macrosomia for the five sequential weight groups were 0.6, 1.0, 1.3, 1.6 and 2.2. We conclude that pregravid overweight had a significant independent effect on birth weight outcome.