What you can expect

By Mayo Clinic Staff

Noninvasive prenatal testing can be done as early as week 10 of pregnancy.

During noninvasive prenatal testing 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, the likely presence of trisomy 21 in the baby. Trisomy 21 is the most common cause of Down syndrome.

Typically, test results are available within two weeks.

Feb. 23, 2013