The effects of marijuana use during pregnancy. II. A study in a low-risk home-delivery population.

Results from a previous epidemiologic study indicate that marijuana use near term may elevate risk of abnormal progress of labor and meconium staining. We conducted a study of the association of self-reported marijuana use and perinatal problems in a series of 313 women enrolled in a home-birth center. The 41 marijuana users were similar to non-users with respect to most potentially confounding factors, but users had lower mean income and exhibited more tobacco and alcohol use during pregnancy than non-users. Users experienced slightly elevated rates of dysfunctional labor (43% vs. 35% in non-users), precipitate labor (13% vs. 8%) and meconium staining (17% vs. 13%); differences with respect to most other outcomes were smaller or nonexistent. The observed differences were smaller in both relative and absolute terms than those reported by the earlier study, and were little changed upon adjustment for potentially confounding factors (including alcohol use, cigarette use, parity and income). After accounting for statistical variation, the results appear consistent with the earlier findings but further research is recommended.