Prenatal marijuana exposure may pose health risks. (Biomedicine).

Rats that were exposed to a marijuana-related chemical while in the womb show more memory lapses and hyperactivity than unexposed rats do, a study finds. Marijuana-exposure studies in people have been clouded by factors such as a mother's tendency to also smoke tobacco cigarettes or pursue other risky behaviors during pregnancy.

Vincenzo Cuomo of the University La Sapienza in Rome and his colleagues injected several pregnant rats with a drug called WIN55,212-2. In the brain, the drug behaves like tetrahydrocannabinol, the active ingredient in marijuana. Another group of animals received inert injections.

Compared with the unexposed rats, the pups born to mothers that got the drug showed hyperactivity and reduced memory retention in behavioral tests conducted during the first weeks and months of life.

Also, rats exposed to the marijuana-related drug in the womb produced less glutamate, an essential neurotransmitter in the hippocampus, which is a memory-processing center of the brain, Cuomo says.

The study, which will appear in an upcoming issue of the Proceedings of the National Academy of Sciences, doesn't directly translate to people, he cautions. Nevertheless, the findings are in line with some earlier studies pointing to memory problems and hyperactivity among children exposed to marijuana in the womb, the researcher notes. "Our findings suggest that both pregnant and lactating women should avoid using marijuana," Cuomo concludes. --N.S.