What you can expect

Prenatal cell-free DNA screening can be done as early as week 10 of pregnancy.

During the procedure

During prenatal cell-free DNA screening, a maternal blood sample is taken and sent to a lab. The lab analyzes the maternal and fetal DNA in the blood sample. A higher than expected ratio of chromosome 21 sequences indicates, for example, an increased risk of trisomy 21 in the fetus. Trisomy 21 is the most common cause of Down syndrome.

Typically, test results are available in five to seven days.