In utero marijuana exposure alters infant behavior

NEW YORK (Reuters Health) - Infants exposed to marijuana in the womb show subtle behavioral changes in their first days of life, researchers from Brazil report.

These newborns were more irritable than non-exposed infants, less responsive, and more difficult to calm, Dr. Marina Carvalho de Moraes Barros and colleagues from the Federal University of Sao Paulo and colleagues report. They also cried more, startled more easily, and were more jittery. Such changes, Barros and her team say, have the potential to interfere with mother-child bonding.

Barros and her team looked at 561 infants born to adolescent mothers. Twenty-six of them had been exposed to marijuana, as revealed by tests on the mother's hair and the infant's stool. Just one of the mothers had reported smoking pot while pregnant.

Trained examiners, who did not know a child's marijuana exposure status, tested the neurobehavioral responses of all infants. On average, marijuana-exposed infants scored differently on measures of arousal, regulation and excitability compared to the non-exposed infants.

"The needs of the infant with altered neurobehavior can easily add to the stress of a substance-using adolescent parent," Dr. Henrietta S. Bada and colleagues from the University of Kentucky Medical Center in Lexington note in an editorial accompanying the study.

Marijuana's active ingredient, tetrahydrocannabinol, does cross the placenta into the fetal circulation, Barros and her team point out. The drug also has been shown to trigger the expression of the neurotransmitter dopamine, they add, and this could result in long-term alterations in nervous system function.

"It is necessary to counter the misconception that marijuana is a 'benign drug' and to educate women regarding the risks and possible consequences related to its use during pregnancy," Barros and colleagues conclude.

SOURCE: Journal of Pediatrics, December 2006.