A new blood screening test has become available which is designed to identify pregnant patients whose unborn babies are at a higher risk for Down syndrome or 3 other rarer conditions involving the fetal chromosomes. A small amount of fetal DNA can be found in maternal blood, some of which comes from chromosome 21, for example. Since fetuses with Down syndrome, also known as trisomy 21, have an extra copy of chromosome 21, the extra amount of DNA coming from this extra chromosome would be detected. Most importantly, if there is a normal amount of this DNA in the mother’s blood, the chances of her having a fetus with Down syndrome is virtually zero, with companies claiming detection rates of over 99%.
Currently, this screening test is being offered by more than one company. The turnaround time is about 5 to 7 business days, but companies are trying to shorten the waiting period. The screening test has been mostly offered to those at higher risk for fetal Down syndrome, such as:
- Women of advanced maternal age, (35 years old or older at time of delivery)
- Women who have “screened positive” for Down syndrome, Trisomy 13, or Trisomy 18
- Women whose fetuses show ultrasound markers which might be found in Down syndrome, Trisomy 13, or Trisomy 18
- Personal or family history of chromosomal condition, such as in a previous pregnancy, with Down syndrome, Trisomy 13, or Trisomy 18
If these conditions are met, some insurance companies will cover the screening test in high-risk pregnancies, though some will not. For those patients who have to pay out of pocket, the companies are presently negotiating the price and payment options. Currently, the “on average” out of pocket cost is $175-$235. After the screening test has been run, the lab will attempt to have your insurance company reimburse you for some or all of the cost, though this is not guaranteed.
It is extremely important for you to know that this is not a screening test that is meant to replace amniocentesis, which is virtually 100% accurate in excluding Down syndrome in those with a positive screening test or DNA test. Also, although three studies have shown a very reasonable accuracy of this screening DNA test, we may have to wait for more patients to be studied in order to determine the true accuracy of this new screening test.
This screening DNA test is a good fit for some patients, but not for others. We are here to help you make the best decision regarding this screening test for you, your pregnancy, and your family.
John C. Hobbins, MDProfessor of Obstetrics and Gynecology Practice Director, Platte River Perinatal Center