We used the Marion County, Indianapolis, IN data on singleton live births for the years 1988-1994 (N=94,683) to compare the effects of cigarette smoking during pregnancy on the risk of adverse pregnancy outcomes among African American and White mothers. Data was analyzed using stratified chi-squared and logistic regression analysis. Prevalence of smoking was higher among White mothers (28.4%, 95% C.I., 28.1-28.8) as compared with African American mothers(20.8%, 95% C.I., 20.3-21.3); White mothers were also more likely to smoke heavily. We used logistic regression to estimate the effects of smoking on adverse pregnancy outcomes while controlling for the effects of maternal age, education, marital status, prenatal care, WIC participation, parity, birth order, and drug use. Logistic models (Table) showed that both African American and White mothers who smoked had an increased risk of very low birth weight (VLBW, <1.5kg) and intermediate low birth weight(MLBW, 1.5-2.5kg). For both African American and White mothers, the risk of MLBW increased with increasing amounts of smoking. However, for MLBW, the effect of smoking was significantly less for African American compared to White mothers. African American mothers who smoked had an increased risk of VLBW only if they smoked more than 10 cigarettes/day. White mothers who smoked had an increased risk of VLBW; however, there was no evidence of an increased risk of VLBW with increasing amounts of smoking. We conclude that the dose response curve of maternal smoking on the risk of adverse pregnancy outcomes depends both on the race of the mother and on the outcome studied. (NS = not significant)

Table 1
Full size table