A Philadelphia hospital says it is the first in the nation to offer pregnant women a two-test combination that tells them within an hour after its completion whether their baby has Down syndrome.
The new screening at Thomas Jefferson University Hospital involves a first trimester blood test and an ultrasound and can have test results for Down’s syndrome within one hour and as early as 10 weeks into the pregnancy. The first trimester test typically requires a one-week wait for results.
Doctors say the faster turnaround time should give anxious mothers-to-be peace of mind sooner, or allow them more time to decide whether to end the pregnancy.
For women who would not consider abortion, prenatal screening still is important because babies with Down syndrome, the most common chromosomal birth defect, can need specialized care at delivery that affects hospital choice.
“Older women will very much be interested in this screening,” said Dr. Stuart Weiner, director of the Division of Reproductive Ultrasound and the Genetics Program at Jefferson. “But since most Down syndrome babies are being born to women under 35, there’s a good argument that it should be available to everyone.”
He said four women so far have taken the new fast-result screening route at Jefferson this month.
People with Down syndrome, which is caused by an extra chromosome, are born with mental retardation, physical characteristics including a flat facial profile and upward slanting eyes, and around half have heart defects.
Special training required
While risk increases with each year of maternal age — from one in 1,200 at age 25 to about one in 300 at 35 — women under 35 give birth to most Down syndrome babies simply because younger women have more babies.
First-trimester screening for Down syndrome is itself fairly new in the United States — tests traditionally have been done here during the second trimester — though women in Great Britain and elsewhere have had access to it for years.
The first trimester test correctly identifies around 85 percent of Down syndrome pregnancies, compared to around 65 percent with traditional second trimester tests, said Dr. Mark I. Evans of the Institute for Genetics and Fetal Medicine at St. Luke’s Roosevelt Hospital Center in New York.
He said the fast turnaround time hasn’t become widespread because properly reading the ultrasound requires specific training and quality controls that are still developing in many clinics and hospitals.
The blood test looks at levels of a protein called plasma protein A, and a type of the hormone called human chorionic gonadotropin. The ultrasound looks for telltale thickened skin at the back of a fetus’ neck.
The National Down Syndrome Society, an advocacy group, cautions that many women who undergo these tests still will get false-positive and false-negative readings and that they should not feel pressured by health care professionals or others about whether or not to continue their pregnancy, according to spokeswoman Suzanne Elliott Armstrong.
Patients at Thomas Jefferson Hospital who get a positive screening result for Down syndrome will be offered on the same day to have genetic counseling and a definitive — and invasive — diagnostic test called chorionic villus sampling, in which cells are withdrawn from the placenta with a needle.