The influence of maternal hypertension on low birth weight: differences among ethnic populations

To determine the influence of maternal hypertension on the risk of low birth weight among white, black, and Hispanic residents of New York City.

New York City birth certificates, 1988 through 1994, provided data on maternal and infant characteristics. Hypertension was self-reported on birth certificates, and was categorized as chronic or pregnancy-related hypertension. The complication of preeclampsia/eclampsia was also noted. The risk of low birth weight (<2500 grams) for maternal hypertension was determined.

The prevalence of hypertension during pregnancy was 3.8% overall, and was highest for blacks and lowest for whites. Low birth weight rates for white, black, and Hispanic babies were 5.0%, 12.8%, and 7.5%, respectively. Low birth weight rates among hypertensive mothers for whites, blacks and Hispanics were 16.8%, 24.4% and 19.5% respectively. The trends were similar for chronic and pregnancy-related hypertension, as well as for preeclampsia/eclampsia. The relative risk of low birth weight offspring among all hypertensive mothers was highest among whites (3.58, 95% CI = 3.39-3.79), and lowest among blacks (1.99, 95% CI = 1.93-2.06). This trend persisted for chronic and pregnancy-related hypertensive mothers, and those with preeclampsia/eclampsia, after adjusting for other maternal socioeconomic characteristics. Due to the higher prevalence of hypertension among black mothers, the population attributable risk of low birth weight was highest among black babies (557 per 100,000 live births) and lowest among whites (309 per 100,000 live births).

Maternal hypertension is an important risk factor for low birth weight. Its impact, however, differed by race/ethnicity groups.