ATLANTA, Jan. 22 (UPI) -- The number of babies born with organs protruding from their bodies has risen significantly in the last 20 years, and most dramatically in non-Hispanic black mothers under 20, but researchers at the Centers for Disease Control and Prevention say they are not sure of the cause.
Instances of gastroschisis -- a birth defect in the abdominal wall causing intestines or other organs to protrude from the body -- doubled in the United States between 1995 and 2012, according to a new CDC report.
About 2,000 babies are born with the defect each year. The cause of the defect is unknown, but researchers in the 1970s linked young maternal age with gastroschisis.
"It concerns us that we don't know why more babies are being born with this serious birth defect," said Dr. Coleen Boyle, director of the National Center on Birth Defects and Developmental Disabilities, in a press release. "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."
According to the CDC's Morbidity and Mortality Weekly Report, researchers at the agency requested birth data for the years 2006 through 2012 from 14 states that had been used to analyze rates of the defect from 1995 to 2005 in a previous report. When researchers pooled data from 1995 to 2012, it covered about 29 percent of births in the United States for those years.
Overall, the number of cases increased during the 20-year period by 30 percent, from 3.6 per 10,000 births between 1995 and 2005 to 4.9 per 10,000 births between 2006 and 2012. All categories of age and race or ethnicity saw increases in incidence, ranging from a 68 percent increase in white mothers under age 20 to 263 percent in black mothers under 20.
The researchers said the increase is not related to births for teen mothers because, during the same 20 years, the number of teen mothers decreased.
"Gastroschisis is unusual among birth defects in that it disproportionately affects younger mothers, a vulnerable population," reseachers wrote in the report. "The continued increase in age-adjusted prevalence and the pace of the increase suggests that unidentified risk factors might be contributing. Identification of these risk factors is needed to inform public health interventions and reduce prevalence."