The Association Between Impaired Glucose Tolerance and Birth Weight Among Black and White Women in Central North Carolina

Abstract

OBJECTIVE—This study examines the relationship of glucose intolerance during pregnancy to birth weight among black and white participants of the Pregnancy, Infection, and Nutrition Study. RESEARCH DESIGN AND METHODS—This prospective cohort study recruited women from prenatal clinics in central North Carolina at 24–29 weeks’ gestation. A 1-h 50-g glucose challenge test (GCT) and 100-g oral glucose tolerance test (OGTT) were conducted. Impaired glucose tolerance (IGT) was defined as one high value on the OGTT, gestational diabetes mellitus (GDM) as two or more high values, and normal glucose tolerance (NGT) was defined as a low or high value on the GCT screen but no high values on the OGTT. Women with known glucose status and birth outcome information were included in this analysis (n = 2055). RESULTS—Black women with IGT had higher rates of both macrosomia (38.5%) and large for gestational age (LGA) (53.9%) compared with white women (10.0% and 13.2%). Black infants’ birth weights (3,800 g) and prevalence of macrosomia and LGA were significantly higher among mothers with IGT compared with NGT women (birth weight, 3,184 g; macrosomia, 7.0%; LGA, 11.6%). In contrast, among white infants, there was no significant increase in birth weight, macrosomia, or LGA associated with the mother’s glucose tolerance status. In addition, there was no effect of GDM on birth weight in either group. CONCLUSIONS—This study suggests that, independent of maternal prepregnant weight, there may be significant increased risk of macrosomia among black IGT women but not among white IGT women. Further investigations into factors that may contribute to the observed results are needed.