75: Impact of marijuana use during pregnancy on newborn outcomes: results from a matched cohort study


      With increasing legalization and use of marijuana (MJ), well-designed research is needed to inform recommendations related to use in pregnancy. Available data are limited by how MJ users are identified, and high rates of other risk factors in MJ using women including smoking and other drug use, and sociodemographic vulnerabilities. The goal of the current study was to examine the associations between biochemically confirmed MJ exposure late in pregnancy and birth outcomes by comparing a sample of pregnancy marijuana users (ME) with a non-using sample (NME) rigorously matched on other potential risk factors.

      Study Design

      Participants were identified via retrospective chart review of all births (n=20,000+) over a 5-year period within a health system of 5 delivery hospitals in 2 states. MJ exposure was considered to have occurred if a urine drug screen at delivery was positive. Non-positive controls (negative MJ urine drug screens throughout pregnancy, at delivery, and no self-report of use) were selected by matching with an exposed case on delivery year and hospital; maternal age, marital status, race, parity, and medical insurance; and in utero exposure to tobacco, alcohol, benzodiazepines, and opioids. Data were electronically abstracted and included background factors, biochemically confirmed substance exposure, and birth outcomes.


      The final sample contained 330 ME infants and 330 NME controls, largely low income, rural, and Caucasian. Group differences (Table 1) show that ME newborns had significantly worse outcomes than NME newborns including a nearly 200g decrease in birth weight, and doubled rates of low birth weight and preterm birth. MJ exposure did not significantly predict Apgar scores or NICU admission.


      MJ exposure in utero predicted some poorer birth outcomes, especially those likely to impact longer term health and development. Effects could not be attributed to other comorbidities including other drug exposure and sociodemographic risks in this study that involved biochemical verification of self-report of MJ and other drug use. Findings add to the growing body of research linking in utero MJ exposure to adverse birth outcomes, and suggest the possibility of longer-term adverse child outcomes. Women should continue to be encouraged to avoid marijuana use during pregnancy.
      Figure thumbnail fx1