Fetal ultrasound has become so sophisticated that it might be used soon for routine screening for Down syndrome and other chromosomal disorders early in pregnancy.
A national study, involving two local medical centers, is underway to see if ultrasound combined with a simple, maternal blood test is a practical way to screen large numbers of pregnant women for chromosomal defects during the first trimester.
The First Trimester Maternal Serum Biochemistry and Fetal Nuchal Translucency Screening Study will examine 60,000 pregnant women during two years. The study involves 13 medical centers nationwide and is being coordinated by Dr. Laird Jackson at Thomas Jefferson Medical Center in Philadelphia. It is funded by the National Institutes of Health.
Previous studies have already shown that a type of ultrasound examination, called nuchal translucency, can indicate a possible problem with the fetus.
"Nuchal translucency is the little bit of fluid that is seen on ultrasound at the back of the baby's head from 10 weeks and three days to the 13th week of gestation," says Dr. Karen Filkins, director of reproductive genetics at UCLA, one of the local study sites. The other is Cedars-Sinai Medical Center.
An excess of this fluid raises suspicion. "What we suspect is [there is] more difficulty handling how fluid is channeled through the body," she says.
Substances in the mother's blood can also indicate a possible chromosomal disorder. If either of these two exams is suspicious, a woman is then referred for a more diagnostic type of testing, such as amniocentesis or chorionic villus sampling.
"I think the first trimester screening is a real breakthrough," says Filkins. "CVS and amniocentesis are definitive tests. But for the woman who may not want to take that big step but wants some reassurance early in the pregnancy that her risks are relatively low, this is simple, straightforward and noninvasive. The woman [whose test] comes out positive can go on and have the invasive testing."
Studies so far have shown that translucent ultrasound can pick up 90% of babies with Down syndrome.
"The purpose of this study is to see how in practicality [screening] would be set up," Filkins says. "Much has already been done to determine the reliability of the testing. It is already offered as a routine test in other countries."
For information on the study call:
--UCLA Medical Center: (310) 206-4039.
--Cedars-Sinai Medical Center: (877) 644-2867.