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Maternal marijuana use alone does not increase risk for adverse neonatal outcomes

New findings published in Obstetrics & Gynecology indicate no association between maternal marijuana use during pregnancy and adverse neonatal outcomes.

The researchers suggest adverse outcomes attributed to marijuana are attributable to concomitant tobacco use and other confounding factors.

“Despite the fact that hundreds of thousands of women use marijuana in pregnancy, little is known about the effects of marijuana on neonatal outcomes,” Shayna N. Conner, MD, MSCI, from the department of obstetrics and gynecology at Washington University School of Medicine, St. Louis, and colleagues wrote. “We sought to determine the effect of marijuana use during pregnancy on neonatal outcomes and clarify whether any increased risk is attributable to marijuana itself or to other confounding factors such as tobacco.”

The researchers performed a systematic review and meta-analysis of data from 31 observational studies published through August 2015. They compared rates of prespecified adverse neonatal outcomes in women who used marijuana during pregnancy with women who did not using observational studies.

They found marijuana use during pregnancy was associated with an increased risk for low birth weight of less than 2,500 g (15.4% vs. 10.4%; RR = 1.43, 95% CI, 1.27-1.62) and preterm delivery at less than 37 weeks of gestation (15.3% vs. 9.6%; RR = 1.32; 95% CI, 1.14-1.54). Pooled data adjusted for tobacco use and other confounding factors showed no statistically significant increased risk for low birth weight (RR = 1.16; 95% CI, 0.98-1.37) or preterm delivery (RR = 1.08; 95% CI 0.82-1.43). There was also no significant difference in secondary outcomes, birth weight, gestational age at delivery, small size for gestational age, level II or greater nursery admission, stillbirth, spontaneous abortion, low Apgar score, placental abruption, and perinatal death, after adjustment.

“The increased risk for adverse neonatal outcomes reported in women using marijuana in pregnancy is likely the result of coexisting use of tobacco and other cofounding factors and not attributable to marijuana use itself,” Conner and associates concluded. “Although these data do not imply that marijuana use during pregnancy should be encouraged or condoned, the lack of a significant association with adverse neonatal outcomes suggests that attention should be focused on aiding pregnant women with cessation of substances known to have adverse effects on the pregnancy such as tobacco.” – by Savannah Demko

Disclosure: The researchers report no relevant financial disclosures.