Women who take Prozac (fluoxetine) while pregnant are more than twice as likely to give birth to a baby with minor defects.

The key phase of the pregnancy has been pinpointed to the third trimester. If the woman was still taking the drug at that point, the baby could be nearly five times more likely to be born prematurely and more than twice as likely to need the help of special care nurseries. The baby also faced nine times the risk of having breathing difficulties, cyanosis (lack of oxygen) on feeding, and jitteriness.

Researchers from the University of California, who made the discovery, are urging all pregnant women taking Prozac to stop the treatment when their pregnancy reaches the third trimester, and ideally when they become pregnant.

Overall, women on the drug were more than twice as likely to give birth to a baby with three or more minor anomalies than women in the general population not taking the antidepressant.

The study involved 228 women taking Prozac who contacted the California Teratogen Information Service, and their pregnancies and births were compared with women who had contacted the service with queries about other drugs.

The results were a surprise because other trials of antidepressants had failed to pick up the risks. One trial had found that 97 per cent of babies born to Prozac taking mothers were born perfectly healthy.

!ANew England Journal of Medicine, 1996; 335: 1010-5.