Screening for some of the common chromosome abnormalities is now available by taking a sample of mother’s blood and looking for DNA (genetic material from her pregnancy). These tests are often called “non-invasive prenatal testing" (NIPT) or “prenatal cell-free DNA screening" (cfDNA).

These tests can tell us the chance, or likelihood, that a baby may have certain types of chromosome abnormalities including Down syndrome, trisomy 18 and trisomy 13. There is also the option to screen for sex chromosome abnormalities.

Cell-free DNA screening can only show if there is an increased chance for certain chromosome abnormalities. It does not screen for all known chromosome abnormalities and is not considered diagnostic. The accuracy depends on the condition, but cfDNA screening appears to be more accurate than traditional screening tests such as the sequential screen and the quadruple marker screen.

Results generally take 10-14 calendar days. A negative result means the chance is small that a baby may have Down syndrome, trisomy 18 or trisomy 13. A positive result means there is an increased chance; definitive testing, such as chorionic villus sampling (CVS) or amniocentesis, will be offered. Some women who do this test will not get results and will either be offered further testing or the option to have their blood redrawn.

These blood tests are available for women who are at least 10 weeks pregnant. Most insurance plans will cover cfDNA screening in singleton (one baby) pregnancies that are at an increased risk for chromosome abnormalities. This may be due to maternal age of 35 or over at the time of delivery, abnormal ultrasound findings, abnormal sequential or quadruple marker screening, or a previous pregnancy with a chromosome abnormality.

These new tests can be complicated. You may benefit from meeting with a prenatal genetic counselor to review your screening options. Genetic counselors are trained medical providers who can discuss the pros and cons of screening and support you in your decision-making.