PITTSBURGH — Megan Norris, who lives outside Pittsburgh, has battled severe heroin and fentanyl addiction for more than a decade. When she relapsed during her pregnancy earlier this year, Norris knew the opioids she was buying on the street likely contained something new and toxic: xylazine "It was the beginning of my pregnancy," Norris said. "Xylazine is so addictive, so physically addictive, you just can't stop.

It's like the flu times a hundred. I was throwing up a lot. I was just in a rotating pit of hell.

So I was using." Drug overdoses are already a leading cause of death for pregnant women in the U.S.

Research shows as many as 1 in 20 women use addictive substances at some point during their pregnancies. A study by the National Institutes of Health found "substance use during pregnancy is prevalent." Opioid use by pregnant women had already quadrupled before fentanyl hit, according to the Centers for Disease Control and Prevention .

Now, public health experts warn that xylazine poses a fast-growing threat to women, their fetuses and newborns. "Almost 100% of our drug supply is fentanyl and 80% to 90% of that fentanyl is adulterated with xylazine," said Dr. Elizabeth Krans, a physician and researcher at UPMC Magee-Womens Hospital in Pittsburgh.

Krans is one of the country's leading experts on pregnancy and drug addiction. She said the impact of xylazine is like nothing she's seen before. "Patients coming in with really intense wounds that add a layer of pain and disco.