A new prenatal screening option that gives pregnant women advance notice about a common genetic condition can come with a big price tag and a little bit of controversy.
Amniocentesis is still the gold standard and a reliable check for the kind of chromosome abnormalities that cause Down syndrome and other health conditions, but many moms decline that test because it requires a needle stick in the belly and carries a small risk for miscarriage.
The new option looks for fetal DNA circulating in the mother’s blood.
“Amniocentesis cannot be done before 15 weeks. With this test we can know in the first trimester,” said Deborah Driscoll, an obstetrician-gynecologist and geneticist at the University of Pennsylvania.
The first-trimester test is marketed under the brand names Harmony and MaterniT21.
Other early screening is accurate about from 80 to 95 percent of the time, Driscoll said, while the blood test option has a detection rate greater than 98 percent.
“It means very few women will receive a positive test result and not be caring a fetus with Down syndrome,” she said.
That certainty — and giving moms reliable results earlier — has some wondering if more women will opt to end their pregnancy.
“I really don’t think of it as a controversy,” Driscoll said. “I think one of the concerns that some geneticists and ethicists have is that we want to be sure that women give informed consent. That this is not viewed as a routine laboratory test. Every physician or counselor that offers this explains to the patient what the test is for, what are the limitations for the test and what it can potentially disclose.”
Preparing for medical concerns and joys
“The test gives parents opportunity to prepare and educate themselves, it’s not just a test to determine whether the person is going to go forward with the pregnancy or not,” said Rose Townsend.
Townsend, the mother of a 7-year-old son with Down syndrome, and her husband founded the Montgomery County Down Syndrome Interest Group. The nonprofit is working to make sure families get information on the medical concerns linked to Down syndrome and some of the joys.
People with Down syndrome often have mild to moderate intellectual disabilities and some physical health problems, including congenital heart defects that can shorten life.
“The list of possible medical concerns can be overwhelming,” said Townsend, a 37-year-old mother of three. “I think it needs to be offset by the equally important information about what life is like for families.”
Right now, the new prenatal blood test is only for pregnant women older than 35 and others with a higher risk of delivering a baby with Down syndrome.
Penn Medicine began offering the test in January.
“Cost is an issue, and for some women that may help them decide whether they are going to have it or not,” said Driscoll, chair of Penn Medicine’s Department of Obstetrics & Gynecology.
The new test is often not covered by insurance; when it is, the co-payment can run from $300 to $500.
During amniocentesis a needle is carefully inserted into the placenta to capture DNA in the fluid surrounding a fetus. The placenta also releases short fragments of DNA into a mother’s blood stream. The new blood test counts that circulating fetal DNA and looks for signs of the chromosome abnormality — trisomy 21 — that causes Down syndrome.
Doctors call it “trisomy” when there are three copies of a certain chromosome instead of the expected two.
The new blood test can’t hunt for signs of other genetic disorders such as cystic fibrosis. While it offers highly accurate results, it is only first-step screening and not a diagnosis.
When the test suggests Down syndrome, Driscoll usually recommends follow-up amniocentesis and other definitive tests. When the blood test shows no signs of Down syndrome, moms can often avoid amniocentesis.
“I think most women who opt to have the screening test will feel very, very reassured,” Driscoll said.