More than a third of pregnant women are prescribed medications for which there is no evidence that they’re safe to use during pregnancy, investigators report.

Moreover, nearly 5 percent of pregnant women are prescribed medication that is known to pose a risk to a developing fetus.

Dr. Susan E. Andrade of the University of Massachusetts Medical School in Worcester, and colleagues accessed automated databases of eight health maintenance organizations and analyzed data on 152,531 women who delivered an infant between 1996 and 2000.

A drug other than a vitamin or mineral supplement was dispensed in the 270 days before delivery to 64 percent of women, the team reports in the American Journal of Obstetrics and Gynecology.

Drugs for which human safety during pregnancy has not been established were dispensed to 37.8 percent, and drugs that are risky for the fetus but which may be acceptable because of the benefits were dispensed to 4.8 percent.

Drugs that are absolutely contraindicated in women who are pregnant were given to 4.6 percent.

The researchers comment that “computerized physician order entry with decision support provides the potential to prevent or warn against the prescription of drugs with known fetal risks.”

Until such systems are more widely available, they conclude, routine medication audits and physician education may help to detect potentially risky prescribing.

SOURCE: American Journal of Obstetrics and Gynecology, August 2004.