Higher risk of birth defects with opioid use in early pregnancy

Women taking opioids, such as Oxycontin, Vicodin, and Percocet just before or during early pregnancy are 2 times more likely to have a pregnancy affected by a neural tube defect, such as spina bifida, according to a study published online September 9 in Obstetrics & Gynecology in advance of the October 2013 print issue.

“In our study we found that use of opioids just before or during early pregnancy was reported by 1.6% to 4% of the mothers,” said study author Mahsa Yazdy, a postdoctoral associate at Slone Epidemiology Center at Boston University..

The study used data from the Slone Epidemiology Center Birth Defects Study, a case-control study that aims to understand the causes of and risk factors for birth defects. For this study the researchers focused on the years 1998 through 2010 and during this time participants were chosen from Philadelphia, San Diego, Toronto, Massachusetts state, and New York state.

As part of the study, mothers were interviewed by telephone within 6 months of delivery about sociodemographic factors and their exposures during pregnancy. The cases consisted of 305 infants with neural tube defects, which included cases with spina bifida, anencephaly, and encephalocele. Two control groups for this study were used; the first control group consisted of 7,125 infants with no major malformations and the second control group was comprised of 13,405 infants with a wide range of birth defects.

“We compared the distribution of periconceptional opioid exposure between mothers of cases and mothers in the 2 control groups. We used logistic regression models to calculate relative risks adjusted for potential confounders,” Yazdy said.  

“The reasons reported for taking opioids varied, but the most commonly-reported reason was for pain and the most frequently-reported opioids were codeine, oxycodone, and hydrocodone,” she said.

“Our key finding was that mothers who used opioids in the first 2 months of pregnancy were 2 times more likely to have a pregnancy affected by a neural tube defect than mothers who didn’t report using opioids during those months.”

While this risk is elevated, it should be kept in perspective, according to Yazdy.

“The risk of a neural tube defect among babies whose mothers did not take opioids is about 2.6 per 10,000 births and among women who take opioids we found the risk increases to 5.9 per 10,000 births; therefore, even though we found a doubling in the risk of neural tube defects, these are still rare occurrences,” she said.

The effects of opioids on a pregnant women and her unborn baby are not well understood but some previous studies have suggested an increased risk of neural tube defects among women who use opioids in early pregnancy.

“It is for this reason that we decided to assess whether treatment with opioid medications was associated with an increased risk of neural tube defects,” Yazdy said.

The key message for healthcare providers is that “they must weigh the benefits of opioid medications along with their potential risks when discussing treatment options with patients who are or may become pregnant, including reproductive-age women who are not planning a pregnancy but might be at risk for unintended pregnancy,” Yazdy said.