Why it's done

Prenatal cell-free DNA screening is available to anyone who is pregnant. It can be used to screen for certain chromosomal disorders, including:

• Down syndrome (trisomy 21)
• Trisomy 18
• Trisomy 13

It can also be used to screen for fetal sex.

Some prenatal cell-free DNA screening tests might also screen for the increased chance of:

• Trisomy 16
• Trisomy 22
• Triploidy
• Sex chromosome aneuploidy
• Certain disorders caused by a chromosomal deletion (microdeletion syndrome)
• Certain single-gene disorders

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).

Keep in mind, however, that prenatal cell-free DNA screening has been shown to be less effective if you:

• Are pregnant with multiples
• Have a body mass index of 30 or higher (obesity)
• Are pregnant via a donor egg
• Are pregnant as a gestational carrier
• Are less than 10 weeks pregnant
• Are taking certain blood thinners

About 1% to 5% of prenatal cell-free DNA screening tests don't yield any result, possibly due to the sample not having enough DNA or other material necessary for the test. In these instances, your health care provider will discuss your options with you.