Opioid painkillers are being prescribed to a large number of reproductive age women.

New findings suggest more than a third of women of this age enrolled in Medicaid, and more  than a quarter of those on private insurance are prescribed opioid painkillers every year, the U.S. Centers for Disease Control and Prevention reported.

"Taking opioid medications early in pregnancy can cause birth defects and serious problems for the infant and the mother," said CDC Director Tom Frieden, M.D., M.P.H.  "Many women of reproductive age are taking these medicines and may not know they are pregnant and therefore may be unknowingly exposing their unborn child.  That's why it's critical for health care professionals to take a thorough health assessment before prescribing these medicines to women of reproductive age."

To make their findings the CDC looked at information from two larger health insurance claim datasets taken between 2008 and 2012; one included women between the ages of 15 and 44 years of age who were enrolled in Medicaid and the other looked at women of the same demographic with private insurance. They found an average of 29 percent of the women on Medicaid and 28 percent of those on private insurance filled an opioid prescription from an outpatient pharmacy each year.

Previous studies of opioid use in pregnancy suggest the drugs can increase the risk of  neural tube defects, congenital heart defects and gastroschisis in babies. There was also found to be a link between neonatal abstinence syndrome (NAS) and opoid use during pregnancy; this condition occurs when offspring experiences withdrawal symptoms from a medication or drug taken by their mother while they were in the womb.

"Women, who are pregnant, or planning to become pregnant, should discuss with their health care professional the risks and benefits for any medication they are taking or considering." said Coleen Boyle, Ph.D., Director of CDC's National Center on Birth Defects and Developmental Disabilities. "This new information underscores the importance of responsible prescribing, especially of opioids, for women of child bearing age."

The findings were published in this week's Morbidity and Mortality Weekly Report (MMWR