Cell-free fetal DNA (cffDNA):
In human pregnancy, the constant turnover of villous trophoblasts results in the release of material into the maternal circulation. This material includes cell-free (cf) DNA, which is commonly referred to as “fetal," but is actually derived from the placenta. During pregnancy, cell-free fetal DNA (cffDNA) released by the placenta and circulating in maternal blood typically reflects the genetic makeup of the developing fetus. cffDNA is present in a pregnant woman's blood in small quantities starting in the first trimester and increases throughout pregnancy.
Approximately 11 to 13 percent of the cell-free DNA in maternal blood is of fetal origin. The amount varies widely from one pregnant woman to another. cffDNA is present after five to seven weeks gestation and increases as pregnancy progresses. Usually the amount of cffDNA peaks between 10 and 20% of the cell-free DNA at 10 to 21 weeks of gestation. The amount of cffDNA is affected by maternal body mass index, gestational age, fetal aneuploidy, and whether the gestation is a singleton or multiple pregnancy. The quantity of cffDNA in maternal blood diminishes rapidly after childbirth. Within two hours after delivery, cffDNA is typically no longer detectable in maternal blood.
Note: Since cell-free DNA (cfDNA) includes cell-free fetal DNA (cffDNA), the terms cfDNA and cffDNA have been used interchangeably to describe NIPT testing. For the purpose of this course, either term can be used to describe NIPT tests!
