Birth outcome from a prospective, matched study of prenatal crack/cocaine use: I. Interactive and dose effects on health and growth

Objective. This prospective, longitudinal project was designed to determine the effects of prenatal cocaine use on the pregnancy outcomes of women from a historically understudied rural public health population. Methodology. We interviewed over 2500 women prenatally, identified 154 cocaine users, and matched 154 controls on race, parity, socioeconomic status, and location of prenatal care (that related to level of pregnancy risk). Drug testing was required at enrollment and at delivery; detailed demographic, psychosocial, and drug histories were taken at each available trimester and follow-up visit. After birth, neonatal nurse practitioners, blinded to maternal history of drug use, examined infants to assess gestational age and take growth measurements. Medical charts were reviewed and the Hobel Risk Scale was completed. Results. Compared with controls, the cocaine users had significantly higher Hobel Prenatal and Total Risk Scores and more preterm infants (28 vs 14), but not a significantly greater number of fetal deaths (3 vs 1). After controlling for the effects of marijuana, alcohol, and tobacco use, the following results remained. There was no difference in gestational age, Ponderal Index, birth weight, or length between infants born to cocaine users and controls. There was a significant interaction effect such that infant head and chest circumference were smaller in cocaine users who also smoked tobacco. Significant correlation coefficients demonstrated the effects of the amount of drug usage on fetal growth during each trimester of pregnancy. The average cocaine use per day for trimesters one and three and for the entire pregnancy was negatively related to birth length. The mean amounts used in trimesters two and three were negatively related to head circumference. Amounts of tobacco and alcohol use in pregnancy were also inversely related to fetal growth measures. When the effects of marijuana, alcohol, and tobacco were partialed out, there continued to be a negative relationship between the amount of cocaine used in the third trimester and infant length and head circumference. Conclusions. The observed decrement in fetal growth, especially head circumference, among cocaine-exposed neonates raises concerns about later growth and development. Follow-up of these infants will reveal if these disadvantages continue. These early results also emphasize the importance of considering amount and time of drug exposure as well as the interactive effects of drug exposure and other risk variables.