Fifteen-fold increase in newborn opioid withdrawal in Ontario

The majority of those babies were born to women who were legally prescribed an opioid both before and during pregnancy, said Dr. Suzanne Turner, a family physician at St. Michael's Hospital and lead author of the study, which used data from the Institute for Clinical Evaluative Sciences (ICES).

As their due date got closer, many of the women shifted from prescription opioids such as codeine or OxyContin to methadone, which in Canada is prescribed almost exclusively to people addicted to painkillers. In recent years, addiction to prescription opioids has supplanted heroin addiction as the most common reason to treat someone with methadone.

"Our findings suggest that most pregnant women treated with methadone over this time period were addicted to prescription opioids, not illegal drugs such as heroin, which is the common perception," said Dr. Turner, who specializes in providing obstetrical care for women with addictions.

The researchers found the incidence of newborn opioid withdrawal, or neonatal abstinence syndrome, grew from 0.28 per 1,000 live births in Ontario in 1992 to 4.29 per cent per 1,000 live births in 2011.

Most of the increase occurred in the final five years of the study, when 1,901 infants were diagnosed with neonatal abstinence syndrome. Nearly half of them were born to women who were eligible for publicly funded prescription drugs at the time of delivery and whose anonymized prescription records could be studied.

Of those women, 67 per cent received an opioid prescription in the one to two years before delivery, 80 per cent in the year to 100 days before delivery and 70 per cent in the 100 days before delivery.

There was a shift to methadone from other opioids as delivery approached, from 29 per cent of the women having been prescribed methadone one to two years before delivery to 53 per cent in the 100 days before delivery. Conversely, the number of women prescribed non-methadone opioids dropped from 23 per cent at one to two years before delivery to 11 per cent in the 100 days before delivery.

"While the women's original prescriptions for opioids may have been inappropriate, the fact that many of these women are being switched to methadone is a good thing," Dr. Turner said.

While babies born to mothers who misuse opioids are more likely to be premature, have low birth weights and high mortality rates, women who have switched to methadone are more likely to deliver babies at term and at higher birth weights.

This study also found that women prescribed opioids during the 100 days prior to delivery were more likely to undergo a Caesarian section and their babies had longer hospital stays and more outpatient physician visits. Neonatal opioid withdrawal is a treatable condition but it can require care in a neonatal intensive care unit and that can impact mother-child bonding.

Dr. Turner said physicians should consider the risk of addiction before prescribing opioids to all patients, especially women of child-bearing age. As well, women of childbearing age should receive counseling that the use of any opioid during pregnancy can cause neonatal withdrawal, especially since unplanned pregnancies are common among women with addictions.