What is a fetal fraction?

Fetal fraction is a term used in non-invasive prenatal testing (NIPT) to describe the proportion of cell-free fetal DNA in a pregnant woman's bloodstream. During pregnancy, a small amount of the fetal DNA is released into the mother's bloodstream, where it can be detected and analyzed for genetic abnormalities.

Fetal fraction is an important factor in the accuracy of NIPT results, as a higher fetal fraction typically results in more reliable test results. A fetal fraction of at least 4% to 5% is generally considered sufficient for accurate NIPT results.

Several factors can affect the fetal fraction, including gestational age, maternal weight, and placental function. Women with higher body mass index (BMI) or at an earlier gestational age may have lower fetal fractions, which can impact the accuracy of NIPT results.

Monitoring fetal fraction during NIPT testing can help ensure accurate and reliable results, allowing healthcare providers to provide proper care and counseling to pregnant women.