Prenatal cell-free DNA screening can be used to screen for fetal sex, fetal rhesus (Rh) blood type and certain chromosomal disorders, including:
- Down syndrome (trisomy 21)
- Trisomy 18
- Trisomy 13
Some prenatal cell-free DNA screening tests might also screen for the increased chance for:
- Trisomy 16
- Trisomy 22
- Sex chromosome aneuploidy
- Certain disorders caused by a chromosomal deletion (microdeletion syndrome), such as Prader-Willi syndrome
- Certain single-gene disorders associated with abnormalities of the skeleton or bones
Prenatal cell-free DNA screening might be more sensitive and specific than traditional first and second trimester screening, such as the first trimester screening and the quad screen. In addition, prenatal cell-free DNA screening might help women who have certain risk factors make decisions about invasive testing that carries a slight risk of miscarriage, including amniocentesis and chorionic villus sampling (CVS).
If you are pregnant and are not significantly obese, your health care provider will explain to you the possible benefits of prenatal cell-free DNA screening. He or she might recommend prenatal cell-free DNA screening if:
- You have risk factors for having a baby who has a chromosomal condition. Risk factors might include older maternal age or having previously given birth to a baby who has Down syndrome, trisomy 13 or trisomy 18. Your health care provider might also recommend prenatal cell-free DNA screening if you've received worrisome results from another prenatal screening test.
- You have an Rh negative blood type. Prenatal cell-free DNA screening can determine the Rh factor of the fetus. If you're Rh negative and the fetus is Rh positive, you might produce Rh antibodies after exposure to fetal red blood cells. This is typically not a concern during a first pregnancy, but can be a concern during subsequent pregnancies.
Keep in mind, however, that prenatal cell-free DNA screening has been shown to be less effective if you are:
- Pregnant with multiples
- Pregnant via a donor egg
- Pregnant and a gestational carrier
- Less than 10 weeks pregnant
If you are obese, your health care provider will discuss other screening methods with you.