Prevalence of marijuana use during pregnancy. A pilot study.

We examined the prevalence of marijuana use in a group of pregnant women using a qualitative, rapid urine screen to detect marijuana metabolites. Between July 1, 1987, and Aug 15, 1987, 322 consecutive patients underwent an anonymous urine toxicology screen at the time of admission to the labor-and-delivery unit. Patients were identified only by a consecutive number and by their age, race, marital status, gravidity, parity and obstetric service (clinic vs. private). The prevalence of positive urine toxicologic screens for marijuana was 19.9% among the study population (64 positive tests among 322 women screened). The prevalence was greater among the clinic patients than the private patients (52 of 161, or 32.3%, vs. 12 of 161, or 7.5%, respectively). The distribution of race and marital status among the marijuana-positive and -negative groups were also significantly different. Specifically, the proportions of black and single women were higher among the marijuana-positive group. Our findings suggest that marijuana use is common in our obstetric patients. The possible association between marijuana use during pregnancy and perinatal morbidity, as well as the unreliable nature of patient drug histories, may support the use of rapid, inexpensive screening techniques, especially if general screening is considered.