Simple, non-invasive prenatal screenings have become a routine part of prenatal care.
These screens can identify the possibility of genetic abnormalities — such as Edwards syndrome — early in the first trimester, allowing women to make informed decisions about how they wish to proceed with their pregnancies.
But a troubling new investigation by Elizabeth Daley of the New England Center for Investigative Reporting, suggests that these screens can be faulty and have led women to terminate healthy pregnancies when they’re faced with the idea of undergoing additional, and often more invasive, testing to absolutely confirm the diagnosis in their fetus.
“The key is understanding the difference between a diagnostic test and a screening test,” says Dale Bearman, MD, an OB-GYN and former chief of staff at Atlanta’s Northside Hospital.
Bearman tells Yahoo Health that the results of a screening test should not lead to an immediate termination — “that’s not the purpose of the test” — and that screening tests are “intended to reduce the need for risky diagnostic tests when the combination of noninvasive screening tests suggests reassuring information.”
Related: How My Miscarriage Changed My Next Pregnancy
A study by Natera, the maker of the Panorama-brand prenatal screening test, concluded that, 22 women out of 356 who were told their fetuses were at high risk for some abnormality terminated the pregnancy without getting an invasive test to confirm the results.
“As in every other situation, we cannot utilize a screen as a diagnostic test because it is more convenient and less risky,” says Bearman. ”Clearly this distinction [between screening tests and diagnostic tests] needs to be addressed.”
These screening tests, frequently not covered by insurance, can cost several thousands of dollars, offering DNA analysis that “reads” the placental DNA present in the mother’s on blood, thus allowing for a crude fetal chromosomal analysis.
Daley, the researcher who conducted the months-long investigation, tells WebMD that “this is supposed to be a risk-based test, not a diagnostics test. It is supposed to tell the woman … you have a higher risk of (your baby) having this.”
Testing placental DNA, however, is not the same as testing fetal DNA, which is why, should a screening test come back positive, additional testing — ranging from amniocentesis to diagnostic ultrasound — is needed to confirm whether there is some kind of chromosomal defect present in the fetus.
Down syndrome, for example, impacts chromosome 21, while Edward’s syndrome, a rarer genetic disorder, effects chromosome 18. When considering the results of these screening tests, it is critical to remember that, as Daley says, “the rarer the condition in a population, the more false positives you are going to have.” She also adds that the tests are more likely to be predictive in “high-risk” populations (such as women of advanced maternal age) than in the general population.
