Many of our patients may have heard about new screening methods for detecting fetal chromosomal abnormalities during pregnancy. The term for this is called noninvasive prenatal screening. This testing can detect Down syndrome (trisomy 21) and other chromosome abnormalities, including trisomy 18 and 13. Over the past few years, there has been quite a bit of emerging technology, data and recommendations regarding the uses, benefits and limitations of such testing.

The information below is to help you understand what this testing is, as well as provide you with the most recent updates on recommendations from the American College of Obstetricians and Gynecologists.

Noninvasive prenatal screening uses cell-free DNA from the blood of pregnant women. Cell-free fetal DNA is fetal DNA that is circulating freely in the maternal blood stream. During pregnancy, the mother’s blood contains fragments of the developing baby’s DNA. This DNA originates from the cells called trophoblasts that make up the placenta. The test analyzes DNA in a sample of the mother’s blood to predict the risk of Down syndrome (trisomy 21), as well as trisomies 18 and 13, in the pregnancy.

Cell-free DNA screening is just that – a screening. It is not a diagnostic test. It should not be used to replace the precision obtained with diagnostic tests, such as chorionic villus sampling or amniocentesis.

Cell-free DNA screening does not assess risk of fetal anomalies such as neural tube defects or ventral wall defects. Patients who are undergoing cell-free DNA screening will still be offered maternal serum alpha-fetoprotein screening and/or ultrasound evaluation for risk assessment.

Important points to consider are:

  • Given the performance of conventional screening methods (standard first trimester screening), the limitations of cell-free DNA screening performance, and the limited data on cost-effectiveness in the low-risk obstetric population, conventional screening methods remain the most appropriate choice for first-line screening for most women in the general obstetric population.
  • The cell-free DNA test will screen for only the common trisomies and, if requested, sex chromosome composition.
  • What does this mean for you?

    • This means that our obstetrical patients will still be counseled on and offered the conventional first trimester screening. The noninvasive prenatal screening discussed here can be done in addition to this standard screening, if desired.
    • This additional testing is usually covered by most insurance companies if you are considered a high risk patient (example: you will be 35 years or older at the time of your due date). Many labs that perform this test have low out-of-pocket costs for those patients whose insurance company does not cover the cost.

We would be happy to talk to you at the time of your visit if you have any questions or would like to discuss this option further.