A serious birth defect that leaves a newborn's intestine's dangling outside the body is becoming increasingly common, and health officials aren't sure what's causing it.
Cases of the abdominal wall birth defect, called gastroschisis, have more than doubled in the United States over the past 18 years, the CDC's Morbidity and Mortality Weekly Report revealed.
The condition is most common among teen mothers, especially babies born to non-Hispanic black mothers under age 20.
"It concerns us that we don't know why more babies are being born with this serious birth defect. Public health research is urgently needed to figure out the cause and why certain women are at higher risk of having a baby born with gastroschisis," Coleen Boyle, the director of CDC's National Center on Birth Defects and Developmental Disabilities, said in a press statement.
"This isn't new. I saw cases when I was a brand new trainee long ago, but they were really unusual then," said Dr. James Greenberg, co-director of the Perinatal Institute and director of Neonatology at Cincinnati Children's Hospital Medical Center. "But anecdotally, over the years, most neonatologists would agree we've seen a steady persistent increase in the number of babies we see each year with gastroschisis."
Gastroschisis happens when the intestines extrude from a baby's body through an opening in the abdominal wall near the baby's bellybutton, said Greenberg. Sometimes other organs are involved, too.
Greenberg said during early embryo development, the abdominal contents are outside the body but they continue to develop and retract and finally are surrounded and closed in by the abdominal wall.
With gastroschisis, he said, "Something happens that prevents or interrupts that natural process of the intestines retracting back into the abdomen." He said it's a complicated process and defects in wall closure during fetal development "could be due to hundreds of reasons."
Greenberg told CBS News that good prenatal care can help spot the condition before birth and prepare new parents and caregivers in advance.
"The most important thing is prenatal care. This can be picked up on a routine second trimester ultrasound. An 18-week ultrasound can identify this. For the caretakers, knowing ahead of time is very valuable for these babies."
He said if doctors know an infant will be born with gastroschisis, a baby's intestines can be protected at the time of delivery and health providers with special training can be on hand to care for the mom and baby properly.
The birth defect will also require surgery in the weeks after birth to return the abdominal organs into the baby's body and repair the abdominal wall. Even after surgery, infants with gastroschisis can have problems eating or digesting food.
"We're still trying to figure out how to feed these babies best, to teach them how to eat," said Greenberg.
In some cases, gastroschisis can be life threatening, the CDC report said.
Greenberg said about five to 10 percent of babies born with this condition have significant complications with their bowels but most of them, over time, go on to do well.
"Treatment works when we know ahead of time," he said.
Overall, about 2,000 U.S. babies are born each year with gastroschisis, according to CDC researchers who analyzed data from 14 states, comparing the prevalence of gastroschisis among babies born to mothers of different ages from 1995-2005 to those born between 2006 and 2012.
Experts say more research is needed to understand why.
"While gastroschisis has become more common among non-Hispanic white and Hispanic mothers, this study shows the greatest increases were among younger, non-Hispanic black mothers. We must continue to monitor changes in this birth defect to identify risk factors contributing to these increases and hopefully start to reverse the trend," said the CDC's Peggy Honein, chief of the Birth Defects Branch at the CDC National Center on Birth Defects and Developmental Disabilities.