TORONTO -- A new study of rats suggests that cannabis use during pregnancy may affect human fetus growth.
Researchers at Western University and Queen鈥檚 University said their findings, published Friday in the journal , back up clinical studies that found an association between marijuana use and low birth weight in human babies.
Tetrahydrocannabinol (or THC, the psychoactive ingredient in cannabis that gives the user the 鈥渉igh鈥� feeling) causes a restriction in fetal growth and a reduction in birth weight of 8 per cent, researchers found. Using a rat model and human placental cells, they mimicked daily cannabis use and also found that it led to a decrease, by more than 20 per cent, of brain and liver growth.
Researchers gave the rats a daily injection of 3 milligrams of THC per kilogram of bodyweight. For a pregnant woman weighing 150 pounds, that would mean about 200 mg of THC each day.
鈥淥ver the last decade, cannabis use has progressively increased in pregnant women, in part due to the perception that its usage poses no risk in perinatal life,鈥� the study reads.
Despite cannabis legalization in several jurisdictions including Canada, marijuana use during pregnancy has not been the subject of much research. This study is the first to 鈥渄efinitively support鈥� the claim that THC can have negative effects during pregnancy, the researchers said. Previous clinical studies that found an association were confounded by the socioeconomic status of included patients, they added.
鈥淭his study is important to support clinicians in communicating the very real risks associated with cannabis use during pregnancy,鈥� said co-author David Natale and associate professor at Queen鈥檚 University.
While researchers concede that the 鈥渕echanisms are not well understood,鈥� they were able to determine that THC blocks effective placenta function, preventing oxygen and nutrients including glucose from reaching the developing fetus. Researchers also found that THC exposure may reduce blood flow from mother to fetus.
