What is fetal fraction?

Fetal fraction is the amount of cell-free fetal DNA (cffDNA) present in a mother's bloodstream during pregnancy. It is measured as a percentage of the total cell-free DNA in the mother's blood and is used in non-invasive prenatal testing (NIPT) to screen for certain genetic conditions in the fetus.

The fetal fraction can vary depending on various factors such as gestational age, maternal weight, and the presence of fetal abnormalities. Generally, a higher fetal fraction is preferred for more accurate results in NIPT.

Low fetal fraction can sometimes result in inconclusive or inaccurate test results, as there may not be enough fetal DNA to provide a reliable analysis. In such cases, a repeat test may be recommended.

Overall, fetal fraction is an important factor to consider when interpreting NIPT results and can impact the accuracy of the test. It is typically reported by the testing laboratory along with the screening results.