Twelve percent of low-income women in Pennsylvania filled an opioid prescription several days after a normal birth, even though most of them had no clear-cut medical need for an addictive painkiller, according to a new study.

About 2,600 of those women filled a second opioid prescription up to two months later, even though most had no pain-causing obstetrical condition in their medical records, and some had a history of non-opioid substance abuse, the University of Pittsburgh analysis found.

The study, in the March issue of the journal Obstetrics and Gynecology, sheds light on opioid-prescribing after vaginal birth, a practice that has barely been studied and lacks authoritative guidelines.

"There are many guidelines for managing acute or chronic pain, but not for maternity care," said lead author Marian Jarlenski, a Pitt health-policy researcher. "We have a public health crisis with opioid addiction. We were surprised to see more than 1 in 10 women were going home with an opioid prescription."

Fatal overdoses from opioid pain medication have soared among U.S. women, increasing fivefold between 1999 and 2010, when more than 6,600 died, federal data show.

Among women on Medicaid, the federal-state health insurance program for the poor, about 40 percent fill a prescription each year for narcotic painkillers such as oxycodone, tramadol, or codeine — an even higher rate than for women with private insurance.

Jarlenski and her five coauthors decided to focus on maternity care because it is the most common reason for hospitalization in the U.S., yet "little is known about opioid-prescribing practices after obstetric delivery."

They analyzed records of 164,720 Pennsylvania women on Medicaid who gave birth vaginally — not by cesarean section, which is a painful surgery — between 2008 and 2013. Women who had used opioids during pregnancy or had a history of misusing the drugs were excluded.

To look  for causes of postpartum pain that could warrant an opioid prescription, the researchers tallied how many women had an episiotomy (a surgical cut made to widen the vagina during childbirth); a genital tissue tear or wound; or a surgical sterilization procedure called tubal ligation.

About 18,100 women filled opioid prescriptions within five days of delivering, even though only 5,100 of them — less than a third — had one of the pain-causing conditions. The women who filled a prescription without a clear-cut need for pain relief were more likely to be smokers and have mental health conditions such as depression, the analysis found.

Most of these scripts were for three- to five-day supplies of opioids, but in a minority of cases, women got a month's worth of pills.

Jarlenski said their next study will try to explain the variation in obstetricians' prescribing patterns.

"Are there some providers who always give women a prescription?" Jarlenski asked. "Are there some who never do? What should the balance be?"

The study couldn't determine whether the 2,600 women who filled a second prescription got it from their obstetricians or family physicians. However, only 26 percent of these women had a pain-causing obstetric condition.

Also unknown was whether any of the women got hooked on opioids. But a previous study of privately insured women who had cesarean sections found that about 1 in 300 "became persistent users after filling an initial opioid prescription," the researchers noted.

National medical organizations such as the American College of Obstetricians and Gynecologists have not issued guidelines for using opioids to relieve pain after vaginal delivery — something the Pitt researchers say is needed.

They note that last month, Pennsylvania, in collaboration with the Pennsylvania Medical Society, became the first state to offer recommendations for opioids in obstetric care. The guidelines say non-drug treatments such as heat and sitz baths should be the first approach to relieving postpartum pain, and non-opioid drugs such as ibuprofen and acetaminophen should be the next step. Only as a last resort, "a short-acting opioid can be used for 5 to 7 days."

Owen Montgomery, an author of the guidelines who is chair of ob-gyn at Drexel University College of Medicine, said any physician with a standing order to send vaginal delivery patients home with an opioid prescription is not keeping up with the standard of care for 2017.

"And if a woman with chronic pain is asking for opioids," he said, "adding opioid addiction to the other medical and psychosocial problems she may have is not doing her any favors."