Marijuana use and pregnancy: prevalence, associated characteristics, and birth outcomes

This study examines the prevalence, behaviors, and birth outcomes associated with marijuana use in pregnancy. This was a retrospective cohort from a university-based prenatal care clinic from July 1, 2009 to June 30, 2010. The primary exposure was marijuana use, defined by self-report or urine toxicology. Demographic and outcome data were determined by chart review and analyzed by chi-square test, Fisher's exact test, ANOVA, and logistic regression. Three hundred and ninety-six patients initiated prenatal care during this time frame; 116 (29.3 %) of whom screened positive for marijuana at initial visit. Patients who used marijuana were less likely to have graduated high school (p = 0.016) or be employed (p = 0.015); they were more likely to use tobacco (p < 0.001) or alcohol (p = 0.032) and report a history of abuse (p = 0.010) or depressed mood (p = 0.023). When analyzed via logistic regression, only tobacco use remained associated with marijuana use (adjusted odds ratio (OR) = 3.3; 95 % confidence interval (CI): 1.9-5.9). Birth outcomes were available for 170 (43.0 %) patients. Only 3 (1.9 %) tested positive for marijuana at the time of delivery. Marijuana use was not related to incidence of low birth weight (13.8 % vs 14.0 %, p = 1.00), preterm delivery (17.7 % vs 12.0 %, p = 0.325), or NICU admissions (25.5 % vs 15.8 %, p = 0.139). Prenatal care utilization was equal between marijuana users and non-users. Although marijuana is common among obstetric patients at prenatal care initiation, most cease use by delivery. Marijuana is strongly correlated with cigarette use. We found no differences in birth outcomes or utilization of prenatal care by marijuana exposure.