Expectant parents and their health care providers should not entirely rely on the results of prenatal blood tests that claim to predict the chances a newborn will have a rare and potentially serious disease, the Food and Drug Administration said in a new warning.
These tests – called noninvasive prenatal screening tests – use a blood sample from a pregnant mother to look for signs that her fetus has a genetic abnormality. They tell parents the risk that a fetus has a particular genetic abnormality, but they may be wrong, the FDA said.
The FDA said expectant parents should discuss the pros and cons of genetic screening with a genetic counselor before getting the tests and seek a follow-up diagnostic test if the screening result is concerning.
The diagnostic tests that confirm or rule out a genetic abnormality, such as an amniocentesis, are more invasive than the blood draws used for genetic screening and have a small risk of miscarriage. But the diagnostic tests are more accurate, the FDA said.
The agency said some people have made critical decisions about a pregnancy, including termination, after receiving worrisome results from genetic screening tests, none of which have received FDA approval.
“Without confirming the results with a diagnostic test, there is no way to know whether the fetus actually had the genetic abnormality reported by the screening test,” the agency said in an April 19 statement. “The FDA is aware of cases where a screening test reported a genetic abnormality and a confirmatory diagnostic test later found that the fetus was healthy.”
The FDA’s notice comes several months after the New York Times reported that 85% of positive screening test results for some conditions are incorrect, despite marketing from screening companies about how their tests are “reliable” and bring “peace of mind.”
Prenatal genetic screening tests look for abnormalities that would cause a disorder, such as missing chromosomes or pieces of chromosomes, or extra chromosomes. But while these tests are often accurate for more common conditions like Down syndrome, they are much less reliable for rare diseases, the New York Times report said.
The story highlights multiple women who got diagnostic tests that disproved the scary results of their genetic screening, including the experience of Cloey Canida, a 25-year-old California woman whose genetic screening said with 99% certainty that her baby would have a disease called Patau syndrome. The test is almost always wrong for women of Ms. Canida’s age, her doctor assured her. After more than $1,000 worth of tests, Ms. Canida learned that her pregnancy was indeed healthy.
“I wish that we would have been informed of the false positive rate before I agreed to the test,” she told the Times. “I was given zero information about that.”
A version of this article first appeared on WebMD.com.