Marijuana May Harm Fetus

Smoking Marijuana While Pregnant May Harm Baby's Brain

From the WebMD Archives

March 25, 2003 -- Smoking marijuana during pregnancy may cause lasting behavioral and mental defects in the child. A new study in animals suggests that children who are exposed to marijuana in the womb may suffer from a variety of long-term problems even if they aren't born with obvious birth defects.

Researchers say that although marijuana is the most widely used illegal drug among women of childbearing age, little is known about the side effects of prenatal exposure to marijuana. They say previous studies have produced conflicting results because it's difficult to account for potential contaminants frequently found in marijuana and contributing effects of other drug and alcohol use.

In this study, researchers examined the effects of exposure to an artificial component of marijuana called WIN in the offspring of rats who received the synthetic cannabinoid while pregnant. The mother rats received a daily injection of the drug that was comparable to a low-to-moderate marijuana dose inhaled by a human smoker.

The results are published this week in the Proceedings of the National Academy of Sciences.

Researchers Giampaolo Mereu of the University of Cagliari in Italy, and colleagues compared how these marijuana-exposed offspring compared to others rats in terms of memory and motor activity. They found that the rats exposed to WIN in the womb were significantly more hyperactive than the other rats, but these differences diminished as the rats reached adulthood.

The effects of exposure on the rats' learning abilities were more long lasting. The WIN-exposed rats consistently scored lower than others on learning tests throughout their lives.

Researchers say they also found that WIN interfered with the release of a brain transmitter called glutamate, a key chemical associated with learning and memory processing.

Although these findings have not yet been confirmed in humans, the authors say these effects on brain chemistry and activity are consistent with existing data showing learning problems in children exposed to marijuana while in the womb.

SOURCE: Proceedings of the National Academy of Sciences, March 24, 2003.

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