Surprising rate of opioid use seen among pregnant women

More than 14% of pregnant women were prescribed opioids for pain at some time during their pregnancy, according to a study published online in Anesthesiology.

Given the surprising rate these medications were prescribed to pregnant women, more research is needed to assess the risk of opioids to unborn babies, the study suggests.

Researchers looked at data from a database of more than 530,000 pregnant women enrolled in a commercial insurance plan who delivered their babies between 2005 and 2011. Their median age was 31. The study investigated which opioids were most often prescribed, what pain was most frequently treated, and how the prevalence varied regionally.

Of the more than 530,000 pregnant women, 76,742, or 14.4%, were prescribed opioids at some point in their pregnancy. Most opioid exposures were for short courses of treatment, usually less than a week. The percentage of women who received an opioid in the first and second trimester was 5.7%; in the third trimester it was 6.5%.  Of these women, 2.2% took opioids three or more times during pregnancy. 

In the study, back pain was the most common condition (37%) for which opioids were prescribed, according to the study. Other conditions included abdominal pain, migraine, joint pain, and fibromyalgia. The most commonly prescribed opioid during pregnancy was hydrocodone (6.8%), followed by codeine (6.1%), oxycodone (2.0%), and propoxyphene (1.6%).  Prescription patterns varied regionally, according to the study. Opioid use ranged between 6.5% and 26.3%, with the lowest rate in the Northeast and highest in the South. Arkansas, Mississippi, and Alabama all had prescription rates in excess of 20%.

According to study author Brian Bateman, MD, MSc, assistant professor, Harvard Medical School, nearly all women experience some pain during pregnancy, but the safety of using opioids to manage their pain remains unknown.

“The risks to the fetus of of opioid exposure in-utero are not well defined,” said Dr. Bateman. “Some studies suggest that opioid exposure during pregnancy are associated with an increased risk of birth defects, but studies are conflicting. Our findings motivate further study into the risks and benefits of opioid therapy for pain during pregnancy.”

Prescriptions for opioids increased almost three-fold in the general population, to more than 200 million between 1991 and 2009, according to the National Institutes of Health. This study found the prevalence of opioid use by pregnant women in the United States is significantly higher than in Europe. The rate of opioid use also varied throughout the country with the highest in the South and lowest in the Northeast. 

In a commentary on the study, Pamela Flood, MD. professor of anesthesiology, Pain and Perioperative Medicine at Stanford University, Stanford, Calif., noted that “the risk to the fetus of short-term exposure to prescription opioids under medical supervision is difficult to assess and needs to be carefully examined in future studies.”

Previous studies have had contradictory findings regarding the risk to the baby. An early U.S. study (1959-1965), and later studies from Sweden and Norway, did not find an association between opioid prescription and birth defects. However, a U.S. National Birth Defects Prevention Study (1997-2005) found associations between codeine and other opioids with birth defects, including atrial and ventricular septal defects, hypoplastic left heart syndrome, spina bifida, and gastroschisis in newborns. Additionally, the U.S. national study cites that when opioids are used long-term during pregnancy, “there is a known risk for neonatal opioid dependence and subsequent withdrawal symptoms in the first few days of life.”