Opioids in Pregnancy Stir New Concerns for SPH Researcher

Posted on: June 27, 2014 Topics: epidemiology

Although potential risks to the developing fetus remain largely unknown, doctors are prescribing opioid painkillers to pregnant women with significant frequency, recent studies indicate.

Those findings worry BUSPH researcher Martha M. Werler, whose own research has shown an association between first trimester use of opioids and neural tube defects, which are malformations of the brain or spine, such as spina bifida. Neural tube defects are one of the most common birth defects, affecting more than 300,000 births worldwide each year.

A 2013 study by Werler, professor and incoming chair of the Department of Epidemiology and a senior epidemiologist at the Slone Epidemiology Center, found mothers with neural tube defects reported more use of opioids early in their pregnancies (3.9 percent) than mothers of children without such congenital defects (1.6 percent).

“About half of pregnancies are not planned, so that’s a big chunk of women who may not be thinking about possible risks associated with their behavior.”

That caution comes as new research shows a staggering 23 percent of 1.1 million pregnant women enrolled in Medicaid nationally filled an opioid prescription in 2007 – up from 18.5 percent in 2000. That usage rate, reported in the journal Obstetrics & Gynecology, is the largest to date of opioid prescriptions among pregnant women.

An earlier study published in the journal Anesthesiology found 14 percent of privately insured women received opioid painkillers at least once during pregnancy.

In both studies, the most commonly prescribed opioids were codeine and hydrocodone, with oxycodone among the top four. The drugs were usually dispensed for a week or less, although a small fraction of women were prescribed them longer. Doctors may prescribe the narcotics for discomfort in pregnancy caused by posture changes, weight gain and pelvic floor dysfunction, or more serious ailments. In the two recent studies, opioids were most often prescribed for back pain or abdominal pain.

The Centers for Disease Control and Prevention (CDC) recently launched a “Treating for Two” website that offers guidance to clinicians and expectant mothers on medication use in pregnancy. It notes that medication use generally during pregnancy has surged: nine out of 10 women now take some medication during pregnancy.

Werler spoke about the trend of opioid prescribing and possible implications for pregnant women:

Are you concerned about the studies showing doctors prescribing opioids to pregnant women in significant numbers?

“Yes. Even the proportion in 2000 seems high to me, and the increase makes it that much more concerning.”

What do you think is driving the trend?

“I can think of no condition in pregnancy that has increased in parallel, for which opioids would be prescribed.  This leads me to wonder about over-prescribing.”

How does your own study play into the concerns about opioid use?

“Our study was the third to observe a positive association between maternal use of opioids and neural tube defects.  In our study, the doubling in neural tube defect risk for opioid exposure was not explained by socioeconomic factors or other behavioral factors, such as cigarette smoking, illicit drug use, and low folic acid intake.”

Do we know how opioid use might affect prenatal development?

“Neural tube defects result from a failure of the developing brain or spinal column to fuse properly in very early pregnancy.  Some neural tube defects cause death, while others can impair cognitive abilities, mobility, and kidney function.

“It is not known how opioid use might affect the developing neural tube. We can speculate based on animal studies, which show opioids affecting the fetus at the molecular, cellular and tissue levels — but the bottom line is that we just don’t know.  For that matter, we don’t know the exact mechanism by which folic acid protects against neural tube defects, either.  Unfortunately, there is a gap between epidemiologic studies and basic science in studies of birth defects.”

Are there good alternatives to opioids for pregnant women who need pain relief?

“Acetaminophen, aspirin, ibuprofen and naproxen are the most commonly taken pain remedies.  These medications are not addictive — but their ability to reduce pain may not be sufficient for the most severe situations.  The effects of these non-addictive pain medications on neural tube development have not been thoroughly studied.

“As always, the clinician and patient must make the best choice for the circumstances, taking the health of the mother and fetus into account.”

Submitted by: Lisa Chedekel