TUESDAY, Nov. 18, 2014 (HealthDay News) -- The proportion of women dependent on drugs such as narcotic painkillers or heroin during pregnancy has more than doubled in the past decade and a half, a new study finds, though it still remains below a half-percent of all pregnancies.
The study covers a class of drugs known as opioids, which include prescription painkillers such as oxycodone (Oxycontin) and Vicodin; morphine and methadone; as well as illegal drugs such as heroin.
Dependence on these drugs during pregnancy is linked to several increased risks during delivery, even when compared to women abusing or dependent on non-opiate drugs, explained study senior author Dr. Lisa Leffert, chief of the Obstetric Anesthesia Division at Massachusetts General Hospital in Boston.
Over recent years, experts have noted an alarming rise across the United States in abuse of narcotic prescription painkillers.
"This increase in opioid abuse and dependence in the pregnant population is happening along with that in the general population," Leffert said. "These women were more likely to deliver by cesarean and have extended hospital stays" compared to other pregnant women, she said.
The researchers analyzed national hospitalization data on nearly 57 million deliveries between 1998 and 2011. They looked specifically at pregnancy outcome risks linked to dependence on opioids. They accounted for differences in age, race, payer type (insurance), having multiple births, mothers' preexisting conditions and a past history of cesarean section.
Preexisting conditions included depression, which was five times higher among those with an opioid dependence, as well as alcohol dependence and non-opioid drug dependence, both of which were more than 20 times higher in women dependent on opioids.
According to the new analysis, the percentage of women dependent on opioids during pregnancy more than doubled during that time, from 0.17 percent in 1998 to 0.39 percent in 2011.
The increased risks for mothers dependent on methadone ranged from preterm labor and poor growth in the fetus to an increased risk of stillbirth and maternal death, though the latter were still very rare.
However, the study has several limitations that should be considered, said Dr. Robert Newman, director of The Baron Edmond de Rothschild Chemical Dependency Institute at Beth Israel Medical Center in New York City.
"The study makes no distinction between dependence on appropriately prescribed, medically indicated opioids and that associated with self-administered opioids taken under potentially very hazardous circumstances," he said. "The different consequences for the expectant mother and unborn child are enormous."
For example, methadone or buprenorphine are both opioids that can be safely used in treatment of addiction, Newman pointed out. In fact, he said, methadone maintenance is the most effective known treatment for heroin addiction, including in pregnant women.
The study authors agreed that "we were not able to distinguish between women who were dependent on or abuse prescription opioids, those who were enrolled in opioid maintenance programs [e.g., with methadone or buprenorphine], and those who abused heroin."
However, women dependent on opioids were twice as likely to go into labor early, with 17 percent experiencing preterm labor versus 7 percent among those without opioid dependency. Women dependent on opioids were also 20 percent more likely to require a C-section and 40 percent more likely to have their water break early.
Two types of complications, intrauterine growth restriction and placental abruption, were also more likely -- though still rare -- in women dependent on opioids than not. Intrauterine growth restriction refers to a baby's poor growth in the womb and occurred in about 7 percent of those dependent on opioids and 2 percent of those without a dependency. Placental abruption, in which the placenta comes off the uterus wall before delivery, occurred in about 4 percent of women with opioid dependency and 1 percent of women without dependency.
The risk of stillbirth was also higher among those dependent on opioids, at a rate of 1.2 percent compared to 0.6 percent of stillbirths among mothers with an opioid dependency.
The risk of maternal death during delivery was also higher for mothers dependent on opioids. Although the risk remained very rare (20 of over 60,000 opioid-dependent pregnant women died), the risk was still more than four times that of nonaddicted pregnant women. Similarly, the risk of maternal heart attack was four times higher among women dependent on an opioid, the study found.
Long-term use of opioids during pregnancy can lead to dependence or withdrawal symptoms in newborns in the first few days after birth, noted Dr. Ted Yaghmour, an associate professor of anesthesiology at Northwestern University's Feinberg School of Medicine.
"Importantly," he added, however, "untreated severe pain in the mother may also be harmful to the unborn baby. [So] when a mom has pain during pregnancy, consultation with an anesthesiologist who specialized in pain management may help them plan an opioid-limiting treatment plan," he said.
Both Yaghmour and Leffert said more research is needed to understand possible long-term effects on children whose mothers were dependent on opioids during pregnancy. However, Newman said the "overwhelming conclusion of published studies is that there are no long-term effects" on these children.
Newman also emphasized the importance of treatment for pregnant women with addictions.
"What is absolutely contrary to the interests of all concerned is to vilify the opioid-dependent pregnant woman," he said. "Most importantly, recognize opioid dependence as a chronic medical condition and treat it as such, and treat the patients the same way others who have chronic illnesses are treated."
The findings were published in the December issue of the journal Anesthesiology.
Find out more about opioid addiction at the American Academy of Family Physicians.