(HealthDay News) — Maternal marijuana use is not independently associated with adverse neonatal outcomes, according to a review published in the October issue of Obstetrics & Gynecology.

Shayna N. Conner, MD, from Washington University in St. Louis, and colleagues extracted data from studies that compared rates of prespecified adverse neonatal outcomes in women who used marijuana during pregnancy and women who did not. The primary outcomes were low birth weight and preterm delivery at less than 37 weeks of gestation. Data were included from 31 studies that assessed the effects of marijuana use during pregnancy.

The researchers found that marijuana use during pregnancy was associated with an elevated risk of low birth weight (15.4% vs 10.4%; pooled relative risk, 1.43; 95% confidence interval [CI], 1.27 to 1.62) and with preterm delivery (15.3% vs 9.6%; pooled relative risk, 1.32; 95% CI, 1.14 to 1.54) based on pooled unadjusted data. After adjustment for tobacco use and other confounding factors, pooled data showed no statistically significant risk for low birth weight (pooled relative risk, 1.16; 95% CI, 0.98 to 1.37) or for preterm delivery (pooled relative risk, 1.08; 95% CI, 0.82 to 1.43).

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“The association between maternal marijuana use and adverse outcomes appears attributable to concomitant tobacco use and other confounding factors,” the authors write.


  1. Conner, SN, Bedell V, Lipsey K, et al. Maternal marijuana use and adverse neonatal outcomes: A systematic review and meta-analysis. Obstet Gynecol. 2016;128(4):713-723. doi:10.1097/AOG.0000000000001649.