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Study: First Trimester is Best Time to Screen Pregnant Women for Fetal Down's Syndrome
DENVER (Nov. 9, 2005) — A new study by researchers for the First- and Second-Trimester Evaluation of Risk (FASTER) Research Consortium has found that the most optimal and accurate time to screen pregnant women for the presence of fetal Down's syndrome is during the first trimester. The findings of the study will be published as the lead article in the Nov. 10 issue of the New England Journal of Medicine.
Researchers reported that the combination of nuchal translucency, an ultrasound measurement of the area behind the fetal neck, and maternal blood markers measured at 11 weeks gestation results in the detection of 87 percent of cases of Down's syndrome. The study also reports that a combination of first- and second-trimester markers yielded a 96 percent detection rate for Down's syndrome at 11 weeks gestation.
Down's syndrome is a genetic condition that causes delays in physical and intellectual development and occurs in one out of every 800 births. The chances of fetal Down's syndrome increases with increasing maternal age. Prior to the study's finding, it has been a standard of care for physicians to provide screening and/or diagnostic tests for Down's syndrome during a woman's second trimester of pregnancy.
Currently, the most common screening test for Down's syndrome is the triple or quadruple screen, a series of three or four blood tests. The quadruple screen detects approximately 79 percent of cases of Down's syndrome and is performed between 15 and 21 weeks of gestation. If a patient has a positive quadruple screen, an amniocentesis is offered. Amniocentesis is also commonly offered to women who are age 35 or older at their delivery date.
"When we conducted these studies, we wanted to find the most optimal method to screen pregnant women for the presence of fetal Down's syndrome," said Lorraine Dugoff, M.D., associate professor in the CU School of Medicine's Department of Obstetrics and Gynecology and co-author of the study. "It was our goal to study the effectiveness of first-trimester screening and find the best possible screening test for Down's syndrome."
Dr. Dugoff and her FASTER colleagues performed first- and second-trimester screenings in 38,167 patients nationwide - the largest U.S. study of first-trimester screening to-date. Dr. Dugoff and colleagues at the CU School of Medicine started a first-trimester prenatal diagnosis program in 2003 and approximately 2,500 Colorado women enrolled in the study.
"The program became very popular over the last two years," said Dugoff. "Many women who are 35 years and older are choosing to have first-trimester screening or a combination of first- and second-trimester screening instead of amniocentesis. There are a lot of women out there who want early non-invasive information regarding the status of their pregnancy and we are hearing from them."
All of the centers in this study had special training before they participated. Due to the potential difficulty in measuring the nuchal translucency, it is critical that all centers that choose to offer this type of screening undergo specialized training. This type of training is currently offered through the Maternal Fetal Medicine Foundation.
"Currently all women are offered a second-trimester screening test as a standard of care," added Dugoff. "The results of this study will have quite an impact because it will give pregnant women and their physicians more options for earlier and more effective screening."
The University of Colorado at Denver and Health Sciences Center is one of three campuses in the University of Colorado system. Located in Denver and Aurora, Colo., the center includes schools of medicine, nursing, pharmacy, and dentistry, a graduate school and a teaching hospital. For more information, visit the Web site at www.uchsc.edu.