For women fighting opiate addiction, methadone maintenance during pregnancy helps them stay off drugs - but it may have adverse effects on the unborn baby, investigators report.

“Methadone maintenance offers clear benefits to the pregnant, opiate-dependent woman (decreased use of illicit substances, reduced fetal mortality, etc.), but it is not without adverse consequences for the infant,” said Dr. Lauren M. Jansson from Johns Hopkins University School of Medicine, Baltimore. “This research has additionally found that methadone used during pregnancy has significant effects on fetal neurobehavior that are independent of maternal effects.”

Jansson and colleagues studied 40 pregnant women attending a substance abuse treatment facility, simultaneously monitoring indicators of neurologic functioning in the fetus and the mother’s physiologic responses during high and low methadone levels.

At peak methadone levels, fetuses had significantly slower heart rate and fewer heart rate accelerations than at trough methadone levels - signs of impaired heartbeat regulation. The duration of fetal movements and the total amount of fetal activity were reduced by half at peak maternal methadone levels, the authors report in the American Journal of Obstetrics and Gynecology.

By contrast, mothers responses were the same at high and low methadone levels.

“This raises an ethical question for the care of the pregnant, opiate-dependent woman,” Jansson said.

“The answer to this question lies in the benefit that can be obtained from the ancillary services that can be provided along with methadone maintenance,” she said, referring to services such as prenatal care and parenting training, in addition to substance abuse treatment.

“Methadone maintenance should only be provided during pregnancy in combination with these services, and never in their absence to this group,” Jansson concluded.

SOURCE: American Journal of Obstetrics and Gynecology, September 2005.