Amanda Williammee pauses at the window of the toddler classroom at Horizons day care in Carrboro, N.C., to quietly check on her 2-year-old daughter Taycee.

"I like to peek in on her and see what she's doing before she sees me," Williammee says. "I love watching her — it's too funny."

There's a dance party in progress. Soon, Taycee spots her mom, screams and comes running to the door.

"Did you dance?" Williammee asks, leaning down to her daughter.

It seems to be a pretty typical preschool pickup, but it's not. Tied to the University of North Carolina Medical Center, Horizons is a residential substance use disorder treatment program where mothers undergoing treatment can bring their children. The kids attend school or day care while mothers take classes and go to therapy sessions.

Williammee, now 25, has struggled with addiction since she was a 19-year-old college student. She injected opioids during both her pregnancies and both of her babies were born with neonatal abstinence syndrome — a condition that includes drug withdrawal symptoms like tremors, irritability, sleep problems and high-pitched crying. Williammee remembers that withdrawals were harder for Taycee than they've been for 6-month-old Jayde.

"It wasn't just like we had this two-week period at the hospital of her being sick. It went on for months because she did not sleep," Williammee remembers. In those days Taycee only slept for 20-minute stretches and needed constant swaddling.

On average, a baby is born in withdrawal from opioids every 15 minutes in the U.S., according to recent research. That staggering statistic raises concerns among doctors and social workers — and among mothers like Williammee.

Today, both Taycee and Jayde are developing normally. Still, Williammee wonders about the risk of lasting effects on each child's body and brain.

Research is just beginning to point toward the answers. Recently, an international, multisite study tracked for 36 months nearly a hundred children whose mothers had been in medically-assisted treatment during their pregnancy. Hendrée Jones is executive director at Horizons and co-authored the study. She says the early results suggest there are reasons to be optimistic.

"The children through time tended to score within the normal range of the tests that we had," Jones says.

Dr. Stephanie Merhar, a neonatologist at Cincinnati Children's Hospital, released a separate study after growing increasingly worried the past few years as she treated children coming in for checkups. Her team reviewed the charts of 87 2-year-olds who had been diagnosed with neonatal abstinence syndrome at birth. Each child had been given a standard test for 2-year-olds that evaluated cognitive, language and motor skills — the same assessment used in Jones' study.

Merhar says what her team found was a call to action.

"Most of these children do well, and they do within the normal range," she says. There is still a risk these kids may experience some delays as they continue to grow, she adds, so they should be monitored closely.

The problems Merhar found among children exposed to opioids in utero include about 8 percent who need treatment for strabismus, or lazy eye, by age 3. A number of the children also scored at least one standard deviation below the mean in terms of cognitive, language and motor skills.

The underlying reason for those delays is unclear, she says, and the long-term outlook for the children is still unknown.

Still, exposure to opioids in utero does not appear to be as damaging as some other addictive substances.