There is a new blood test that is taking the world of prenatal diagnosis by storm: noninvasive prenatal testing.  

It can be performed on a pregnant woman as early as 10 weeks gestation, perhaps even before she has announced to family and friends that she’s pregnant. NIPT checks for chromosome conditions such as Down syndrome, Trisomy 13, and Trisomy 18, and for sex chromosome conditions such as Turner syndrome and Klinefelter syndrome, among others. Usually, the biggest risk factor with most of these conditions is the age of the woman: the greater the age, the greater the risk.  

The concept behind this blood test is simple, yet extremely complex. Because the mother and baby exchange blood circulation through the placenta, short pieces of cell-free DNA from the placenta are found to flow through the maternal bloodstream, along with mother’s own DNA. For the patient, the testing is an easy blood draw, usually two tubes. That’s where the simplicity ends and the complexity begins.  

The blood is shipped to a lab, where the maternal and cell-free DNA is isolated, analyzed, divided out, counted, and assigned to a specific chromosome. 

If your mind is already spinning, let’s review high school biology for a bit. Our genetic information is packaged into chromosomes. We have two copies of our chromosomes; and they are labeled one through 22. The sex chromosomes determine gender: XX for a girl; XY for a boy. The most common chromosomal conditions are due to the wrong number of chromosomes, either too many, or not enough.

NIPT screens to see if the baby has the correct number of chromosomes by looking at the free-floating DNA. Too many or not enough pieces of DNA from a specific chromosome means there is an increased risk of a specific disorder. The accuracy of this new testing is greater than 99 percent. One thing to remember about NIPT is to put the pregnancy into a high- or low-risk category, not to diagnose these conditions. Invasive diagnostic testing—chorionic villus sampling and amniocentesis—is offered to anyone who wants the most accurate information available. However, those tests both have a risk of miscarriage. 

As a genetic counselor, I’ve found that most people usually want the most information with the least amount of risk, unless there are suspicious findings on ultrasound. It’s also important to remember that testing is for information only; it’s not for cure, therapy, or treatment.

With this new test, it has been challenging to know exactly how to put it into practical use in the clinic. It has resulted in many questions for clinicians and patients alike. Do we offer this test to everyone, or only high risk patients? Is it a first-line screen or a secondary test? The answers might be simple and straightforward to some patients, but not to others.    

Several professional medical societies, including the American Congress of Obstetricians and Gynecologists, American College of Medical Genetics, and International Society for Prenatal Diagnosis, recommend genetic counseling when considering this test. Some patients might decline NIPT after a thorough discussion with a genetic counselor because they don’t feel it would provide useful information.

There also is some debate as to who should be offered this test. Most everyone in the medical community recognizes NIPT is useful in patients classified as high risk for having a pregnancy with a chromosomal condition. However, some physicians and genetic counselors are offering this test to all patients.  

The world of NIPT will only get more complex. Currently, NIPT checks for about seven chromosomal conditions. What’s next? Some companies are developing blood tests using similar DNA sequencing technology that can check for up to 100 chromosomal and genetic conditions. These tests possibly could be launched in the next year or two. The eventual goal is complete sequencing of the entire fetal genetic code. The question isn’t if this technology will happen; the question is when it will happen.  

While the test isn’t for everyone for a number of reasons, it should be made available to those who want the most accurate information without putting the pregnancy at risk of miscarriage. NIPT has the potential for enabling the patient to be involved in her prenatal care, as she accepts, or declines the test. Ultimately, the goal of NIPT is to offer a safe alternative to invasive testing. Clearly, NIPT will continue to revolutionize prenatal testing options for patients.

Matt Tschirgi is a licensed and certified genetic counselor at Obstetrix Maternal Fetal Medicine at Deaconess Hospital.