Genetic Testing in Pregnancy with Amnio, CVS & NIPT
Genetic testing in pregnancy with Amnio and CVS carries risk of miscarriage, but what about the non-invasive tests that most women have that lead to the recommendation to have an Amnio or CVS?
Right now, genetic testing in pregnancy is undergoing a seismic shift. There are many different tests that are offered to pregnant moms to screen for genetic conditions. These combined and integrated screens rely upon a combination of ultrasound plus a series of blood tests for pregnancy hormones and proteins.
While these tests are much better than just estimating risk and recommending amnio and CVS just based upon a mom's age, they aren't perfect.
Unfortunately, traditional screening carries with it accuracy of 85-95%, but that means that there are various levels of false positive results that an lead to a recommendation of Amnio or CVS. The false positive rate for the most accurate combination of tests is 5%.
Recently, I met a mom, Courtney*, who was one of those moms who had a worrisome combined screening test result that indicated that she was at high risk for having a baby with Down Syndrome. As a result, she had an amniocentesis, which carries a risk of miscarriage of 1 in 300 to 1 in 500.
Risk of Miscarriage with Amnio
Courtney* who was one of the unfortunate moms who was the 1 woman in 300 who did miscarry from the amnio. She came to talk to me during her 4th pregnancy about the new Non-Invasive Prenatal Genetic Testing options. She had 2 healthy children and wanted to avoid the possibility of an amnio.
Why we care about a 5% rate of false positives
Though the number of false positives from combined and integrated screenings are about 5%, and may sound low, that 5% represents 50 women in 1000 who will be asked to have an amniocentesis or CVS, both of which have risks of miscarriage. And of those 50 women, between 47-49 will NOT have an affected pregnancy.
Courtney was one of the women who was in the 5%, who wanted to have conclusive, diagnostic information about the possibility of a genetic condition. It turned out that she had a false positive result and lost a healthy pregnancy.
The issue is that these conclusive, diagnostic tests are available to find the 1 -3 pregnancies in 1,000 with serious genetic conditions, and in order to find those few, many, many more women are asked to have invasive testing.
New testing options
Now there are new genetic screening tests, NIPT, Non-Invasive Prenatal Genetic Testing, such as The Harmony Prenatal Test, available that are much more accurate and have false positive rates that are less than 0.1%. That means that fewer moms will need amnio and CVS and there will be fewer miscarriages as a result.
NIPT - Non invasive prenatal genetic testing is a simple blood test that can be done as early as 10 weeks of pregnancy.
How it works
NIPT looks for the baby's cell free DNA that's circulates in the mom's bloodstream early in the first trimester. By examining the actual DNA from the baby, NIPT provides higher accuracy for screening for the most serious genetic conditions.
Higher accuracy means fewer unnecessary Amniocentesis and CVS diagnostic tests.
*Courtney is not her real name.
Disclosure: After reviewing the research on Non-Invasive Prenatal Genetic Testing, I began working with Ariosa Diagnostics to help educate and inform pregnant women about their range of prenatal testing options, including The Harmony Prenatal Test, which I recommend to my patients as it has the most published research on actual patients and families.