Influence of maternal glucose level on ethnic differences in birth weight and pregnancy outcome.

Minority ethnicity increases the risk of a poor pregnancy outcome in the United States. The mechanism(s) whereby this occurs is unknown. One possibility is physiologic variation in levels of maternal glucose, the major substrate for fetal growth, which is metabolized from the maternal diet and endogenous gluconeogenic sources. The authors examined whether postload glucose concentration at week 28 was associated with maternal ethnicity or altered the ethnic difference in birth weight after adjustment for duration of gestation (to index fetal growth) and pregnancy outcome (large- and small-for-gestational-age births) among 2,072 diabetes-free gravidas in Camden, New Jersey (1990-2001). After data were controlled for potentially confounding factors, maternal glucose level was significantly lower for African Americans than for Hispanics (mainly Puerto Ricans) or Whites. Maternal glucose was associated with infant birth weight to a similar extent within each ethnic group (1.5-2.0 g of birth weight per mg/dl of maternal glucose). A comparison of regression coefficients from models with and without glucose indicated small but statistically significant effects of glucose on the ethnic difference in birth weight and the risk of large-for-gestational-age birth between African Americans and Whites. Maternal glucose concentration did not differ between Hispanics and Whites; consequently, glucose did not influence this ethnic difference in birth weight and pregnancy outcome.