Effects of alcohol use, smoking, and illicit drug use on fetal growth in black infants.

STUDY OBJECTIVES

To compare the effects of prenatal exposure to alcohol, smoking, and illicit drugs on birth size.

DESIGN

Prospective, longitudinal correlational study, with statistical control for confounding.

PARTICIPANTS

Four hundred seventeen black infants. Mothers recruited at first prenatal clinic visit on the basis of moderate-to-heavy use of alcohol or cocaine or both, plus a 5% random sample of lower-level drinkers and abstainers.

MAIN RESULTS

Alcohol, smoking, opiates, and cocaine were each correlated with smaller birth weight, length, and head circumference (median r = -0.21; p < 0.001). However, when all four substances, gestational age, and six covariates were controlled statistically, birth weight related only to alcohol and smoking (p < 0.05), length only to alcohol (p < 0.05), and head circumference only to opiates (p < 0.01). Although smoking affected birth weight at all levels of exposure, a larger deficit was seen in relation to heavy drinking (509 gm) than to heavy smoking (269 gm). Alcohol and smoking did not affect birth size synergistically, and their effects were seen primarily in infants of women more than 30 years of age.

CONCLUSIONS

The association of reduced birth weight and length with illicit drug use may be a consequence of simultaneous exposure of the fetus to alcohol and smoking. Opiate exposure is specifically related to reduced head circumference, and the effect of cocaine on birth size is primarily an indirect consequence of shorter gestation and poorer maternal nutrition.