No one knows why the congenital defect occurs more often now, but UNC School of Medicine scientists suspect that because of its rapid increase, environmental and either legitimate or illegitimate drug exposures may be responsible.
A report on the troubling finding appears in the June issue of the Journal of Perinatology, a professional journal, being published today (May 22).
UNC authors are Drs. Matthew M. Laughon, a fellow in neonatal-perinatal medicine; Carl Bose, professor of pediatrics and chief of neonatal-perinatal medicine; and Ann Heerens, a former fellow now with the Pediatrix Medical Group of Roanoke, Va.. Others are Dr. Robert Meyer and Alison Wall of the N.C. State Center for Health Statistics in Raleigh, Dr. Eduardo Otero of the Broward General Medical Center in Ft. Lauderdale, Fla., and Dr. Reese Clark of the Pediatrix Medical Group in Sunrise, Fla.
"We decided to do this study because we seemed to be getting a lot of referrals to our Center for Maternal and Infant Health of mothers whose babies were born with gastroschisis," Laughon said. "This is an important problem because the mortality rate for these children is somewhere between 3 percent and 8 percent. Pediatric surgeons replace the intestines during surgery, but since they don't work well at first, it takes babies a long time to recover, and many of them will spend an average of 30 to 40 days in the hospital."
The UNC doctors and their colleagues decided to analyze medical information from two large databases, one for North Carolina births and the other for patients across the nation to learn if the incidence of the ailment had changed in recent years. They also contacted all tertiary care centers throughout the state to verify that babies included in the study had gastroschisis and not some other gastrointestinal problem.
"We found the incidence of gastroschisis increased in North Carolina from 1.96 per 10,000 births in 1997 to 4.49 per 10,000 births in 2000," Laughon said. "Over the same span, the rate grew from 2.9 per 1,000 patients receiving care from a national neonatal care provider to five per 1,000 patients treated."
During normal development, infants' intestines develop outside the womb, eventually rotate 270 degrees and then move inside the abdomen, Laughon said. In babies born with gastroschisis, the intestines develop and the rotation occurs, doctors believe, but the vital organs do not move into the abdominal cavity that is supposed to hold them. For some reason, the intestines also tend to be somewhat shorter than average.
Unlike another birth defect known as omphalocele, in which the intestines remain outside but are covered with a membrane although no skin, gastroschisis is not generally associated with other acute problems such as in the heart, brain or kidneys, he said.
Laughon and colleagues found no comparable increase in the incidence of babies born with omphalocele in North Carolina. They did find by far the biggest jump in gastroschisis among mothers under age 20 for reasons that still are unknown.
"Prior to our work, there had been some reports of increasing rates of gastroschisis, but the numbers were small and not statistically significant," the physician said. "Risk factors that have been suggested for the problem include aspirin use, Sudafed use, mothers' smoking and some dietary changes, but no one really knows exactly what's going on."
Laughon, Bose and others, in collaboration with Dr. Andrew Olshan, an epidemiologist with the UNC School of Public Health, and the Centers for Disease and Prevention, are working to establish a birth defects monitoring program that will cover most of central North Carolina.
"This will help us monitor between 80 and 100 different birth defects, and we're going to take an intensive look at gastroschisis to try to figure out why it has jumped so much," Laughon said. "One of the things we'll take a hard look at is the street drug 'ecstasy' since its use among teen-agers is rising."
Note: Laughon can be reached at (919) 966-5063 or matt_laughon@med.unc.edu
Contact: David Williamson, (919) 9652-8596
Embargoed until May 22
No. 283
By DAVID WILLIAMSON
UNC News Services
Journal
Journal of Perinatology