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Published in Obstetrics & Gynecology this month, the authors reviewed 31 studies between 1982 and 2015, evaluated their results, and concluded that cannabis – when used without tobacco or other drugs – posed no significant risks to specific concerns about birth weight and preterm delivery. This was consistent with findings of a 2010 study funded by the CDC.
Up until this point, studies on cannabis and pregnancy have shown somewhat contradictory results regarding birth weight and preterm delivery, a confusion that researchers attributed in part to inadequate separation of confounding variables, or factors that produce correlations even though a causal relationship doesn’t actually exist. For example, cannabis consumption and tobacco use are correlated, making it difficult to tease apart whether one or both contributes to low birth weight or preterm delivery.
The authors wrote:
“We found that maternal marijuana use during pregnancy is not an independent risk factor for low birth weight or preterm delivery after adjusting for factors such as tobacco use. There also does not appear to be an increased risk for other adverse neonatal outcomes such as SGA and placental abruption once we account for other influencing factors.”
The authors of this study concluded that cannabis use during pregnancy is still not something to be “encouraged or condoned.” Why? While this study focused on two specific birth outcomes of mothers using cannabis during pregnancy, it did not look at long-term developmental health or other risks during gestation.
A 2014 study, for example, found evidence that THC exposure during pregnancy affected brain development in both mice and humans. Fetal development is an intricate process involving specifically timed signaling that may be impacted by THC, leading to impairments later in life. Although this newest review may help relax concerns relating to birth weight and preterm delivery, there may still be other complications attributable to maternal cannabis use.
For this reason, most medical professionals still strongly recommended that pregnant women abstain from cannabis use, despite the temptation to use it for nausea and stress during the tumultuous time of pregnancy.