What Mom's Painkiller Means for Baby

Opioids during pregnancy increased risk of neural tube defects in children

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) What a woman takes or eats while pregnant can often have an effect on her unborn child as well. This is especially true for certain medications a woman might take while pregnant.

A recent study found an increased risk for a specific type of birth defect among children of women who took opioids during pregnancy.

Opioids are commonly prescribed painkillers such as hydrocodone and codeine.

Children of women who took these medications during pregnancy were about twice as likely to have a neural tube defect.

The neural tube is the part of a developing fetus that leads to the development of the spinal cord.

"Discuss medication risks during pregnancy with your OB/GYN."

This study, led by Mahsa M. Yazdy, PhD, of the Slone Epidemiology Center at Boston University, looked at the possible effects of opioids on a developing baby in pregnant women.

The opioids included in this study were codeine, oxycodone, hydrocodone, morphine, propoxyphene, meperidine, methadone, tramadol, hydromorphone, butorphanol, heroin, fentanyl, buprenorphine, nalbuphine and diphenoxylate.

The study population came from hospitals in the Boston, Philadelphia, Toronto and San Diego areas.

The researchers first identified 305 babies who had been born with one of three conditions related to neural tube defects. The neural tube is what develops into a person's spinal cord.

These children included 220 with spina bifida, 51 with anencephaly, 30 with encephalocele and one with spina bifida and anencephaly.

In spina bifida, the neural tube does not fully close, leaving it partly exposed. Anencephaly is an absence of a large part of the brain and/or skull.

Encephalocele means a baby's skull does not completely close before birth and a protrusion grows out of it.

These babies and their mothers' pregnancies were compared to two other groups of babies: 7,125 with other birth defects and 13,405 who had been born with no major birth defects.

The mothers were interviewed about their use of cigarettes, alcohol and caffeine during pregnancy as well as their diets, medical history and use of medications and/or vitamins.

They were also asked about their basic characteristics (age, race/ethnicity, income), their occupation and their history of pregnancies or miscarriages.

The researchers looked at how many women had used an opioid during pregnancy within the first two months after her last menstrual period.

They looked at these first two months because the neural tube fully closes in the earliest stages of the pregnancy, usually within a month after conception.

The researchers accounted for a range of other factors in their analysis:

  • the hospital where the baby was born
  • the mother's race/ethnicity
  • the mother's age
  • the mother's level of education
  • the mother's pre-pregnancy weight
  • whether the pregnancy was planned or not
  • whether the mother had gestational diabetes (diabetes occurring only during pregnancy)
  • whether the mother smoked
  • whether the mother regularly took vitamins with folic acid (which is needed for healthy neural tube development)
  • whether the mothers used any street drugs
  • whether the mothers used any other pain medications

The researchers found that 3.9 percent of the mothers with babies with neural tube defects had used opioids during pregnancy.

Further, 1.6 percent of women whose babies had no defects and 2 percent of women whose babies had other (non-neural tube) defects had used opioids during pregnancy.

The average length of time the women had used opioids was 87 days among those who had babies with neural tube defects, 85 days among those whose babies had no defects and 89 days among mothers with babies who had other birth defects.

Even though folic acid is known to reduce the risk of spina bifida, the differences among the groups were not explained by the mother's consumption of folic acid.

The odds that babies would develop a neural tube defect were roughly twice as high if the mother used opioids during pregnancy.

"Overall, our data support a modestly increased risk of neural tube defects associated with maternal [during pregnancy] opioid use," the researchers wrote.

This study's findings cannot prove that the opioids caused the neural tube defects, but it does show an increased risk for these defects among children of mothers who took opioids.

Andre Hall, MD, an OBGYN at Birth and Women's Care, PA in Fayetteville, NC, said obstetricians are very conservative when it comes to prescribing medications to women during pregnancy.

"This often presents difficult dilemmas when dealing with women who are dealing with pain," Dr. Hall said. "Opioids are a common class of medications for the treatment of pain. However, they are category C medications."

The US Food and Drug Administration definition of Category C medication is as follows: "Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks."

Dr. Hall said this study raises the concern of a real link between the use of opioids and neural tube defects in unborn developing babies.

"This further reinforces that for medications in this category, they should only be used when safer alternatives have failed," he said. "They should be used in the smallest effective dose for the shortest possible time in order to obtain the desired pain relief."

The study was published September 11 in the journal Obstetrics and Gynecology. The research was funded by the US Centers for Disease Control and Prevention (CDC).

One author owned study in Johnson & Johnson and serves on the advisory committee of Biogen-Idec, Tysabri Pregnancy Registry.

Another author is on the advisory boards of manufacturer-sponsored studies evaluating pregnancy outcomes for women taking rheumatoid arthritis medication. No other conflicts of interest were reported.

Review Date: 
September 13, 2013
Last Updated:
September 16, 2013