Cocaine use during pregnancy and intrauterine growth retardation: New insights based on maternal hair tests

Prenatal cocaine use is more accurately measured by maternal hair assay tha n by urine toxicology screening or self-report. To investigate the conseque nces of improved measurement, the authors ascertained cocaine use during pr egnancy by maternal hair test, urine test, and self-report in a sample of 6 91 patients recruited from one New York City hospital in 1990-1992. Associa tions with intrauterine growth retardation, head circumference, and length of gestation were investigated. A positive hair test at delivery was not mo re strongly associated with birth weight (-38.1 g; 95% CI: -164, 88.3) or h ead circumference (-1.73 mm; 95% CI: -5.91, 2.44) than a positive urine tes t at delivery (-182 g (95% CI: -295, -69.8) and -6.11 mm (95% CI: -9.99, -2 .24), respectively). Cocaine concentration in hair (which was higher if uri ne tests were positive) had a dose-response relationship with birth weight: a 27-9 decrease (95% CI: -51.9, -1.04) with each log-unit increase in conc entration. Birth weights were similar among infants of never users and infa nts of users who stopped using cocaine before delivery. Heavier use of coca ine, but not lighter use, was associated with intrauterine growth retardati on, and exposure in late pregnancy was necessary to the association. Althou gh maternal hair tests were instrumental in clarifying these relations, the ir clinical use is probably not warranted.