Researchers at The Children’s Hospital of Philadelphia are beginning a study to compare two treatments for a serious condition that may occur in pregnant women carrying twins. In twin-twin transfusion syndrome (TTTS), abnormal circulation between the twins and the placenta they share may cause one twin to be much smaller than the other, and surrounded by much less amniotic fluid. The imbalance in circulation may kill one or both fetuses, or damage the health of twins who survive.
Physicians usually diagnose TTTS using prenatal ultrasound, augmented by other tests such as fetal magnetic resonance imaging and amniocentesis. Although TTTS occurs in only 200 to 1800 pregnancies annually in the U.S., the condition has a disproportionately high impact. In approximately 17 percent of cases in which a twin dies before, during or shortly after birth, the cause is TTTS. Estimates of the frequency of TTTS vary widely because of differing criteria for diagnosing the syndrome.
Timothy M. Crombleholme, M.D., a pediatric and fetal surgeon at the Center for Fetal Diagnosis and Treatment at Children’s Hospital, is the principal investigator of the national, multicenter clinical trial, which is comparing two treatments for TTTS. The current standard treatment is amnioreduction, in which excess amniotic fluid surrounding one fetus is drained through a needle inserted into the mother’s abdomen. Another treatment, laser photocoagulation, uses heat from a laser, inserted through a flexible tube, or fetoscope, to seal off the blood vessels connecting the two fetuses. The goal of the laser treatment is to separate the communicating circulation between the twins which causes the syndrome.
Without prenatal treatment for TTTS, both twins usually die. Even with treatment, survival of both twins is not guaranteed, and survivors are nearly always born prematurely, sometimes with health complications, including brain injury and heart conditions related to the abnormal pre-birth circulation.
Both treatments aim to obtain a more normal balance of amniotic fluid between the twins, although only the laser treatment addresses the underlying anatomical defect. However, the two treatments have not previously been directly compared in a clinical trial.
This study will evaluate which treatment, laser photocoagulation or amnioreduction, results in better survival rates and better cardiac, neurological and developmental outcomes. In addition to studying health outcomes immediately after birth, the researchers also will assess the twins’ neurodevelopment at age 18 to 22 months.
Twelve medical centers throughout the United States will participate in the TTTS trial, sponsored by the National Institutes of Health. While all 12 centers perform amnioreduction, only two, The Children’s Hospital of Philadelphia and the University of California, San Francisco, also perform fetoscopic laser coagulation. Those two institutions also are the only centers in the world offering comprehensive treatments in fetal surgery.
Enrollment for the multicenter TTTS study began in March 2002 and is scheduled to continue through March 2005. Throughout the country, researchers expect to recruit a total of 150 patients for the trial, of which approximately half will be recruited by The Children's Hospital of Philadelphia.
Because of the requirements of randomized studies, each mother who enrolls in the trial will be randomly assigned to either amnioreduction treatment or laser treatment. Participating centers will not perform the laser treatment outside of the clinical trial.
More information about the TTTS study at The Children’s Hospital of Philadelphia is available by calling the Hospital’s Center for Fetal Diagnosis and Treatment at 1-800-IN-UTERO (1-800-468-8376).
Founded in 1855 as the nation's first pediatric hospital, The Children's Hospital of Philadelphia is ranked today as the best pediatric hospital in the nation by a comprehensive Child magazine survey. Through its long-standing commitment to providing exceptional patient care, training new generations of pediatric healthcare professionals and pioneering major research initiatives, Children's Hospital has fostered many discoveries that have benefited children worldwide. Its pediatric research program is among the largest in the country, ranking second in National Institutes of Health funding. In addition, its unique family-centered care and public service programs have brought the 381-bed hospital recognition as a leading advocate for children and adolescents from before birth through age 19. For more information, visit http://www.chop.edu.