Abstract
A paradigm shift in noninvasive prenatal screening has been made with the discovery of cell-free fetal DNA in maternal plasma. Noninvasive prenatal screening is primarily used to screen for fetal aneuploidies, and has been used globally. Fetal fraction, an important parameter in the analysis of noninvasive prenatal screening results, is the proportion of fetal cell-free DNA present in the total maternal plasma cell-free DNA. It combines biological factors and bioinformatics algorithms to interpret noninvasive prenatal screening results and is an integral part of quality control. Maternal and fetal factors may influence fetal fraction. To date, there is no broad consensus on the factors that affect fetal fraction. There are many different approaches to evaluate this parameter, each with its advantages and disadvantages. Different fetal fraction calculation methods may be used in different testing platforms or laboratories. This review includes numerous publications that focused on the understanding of the significance, influencing factors, and interpretation of fetal fraction to provide a deeper understanding of this parameter.
Highlights
Circulating cell-free DNA has been proven to be useful for noninvasive oncological examinations and general medical examinations by numerous studies
This review focuses on the significance and influencing factors of Fetal fraction (FF), and the management of pregnant women with failed noninvasive prenatal screening (NIPS) results due to a low FF
Is FF routinely reported in NIPS reports and is its significance indicated in clinical reports?
Summary
Circulating cell-free DNA has been proven to be useful for noninvasive oncological examinations and general medical examinations by numerous studies. Cell-free fetal DNA (cffDNA), originating from placental tissue and found in maternal plasma, was first reported in [1] and was initially used for fetal sex determination [2]. With the advent of next-generation sequencing, two studies published in 2008 showed that cffDNA can be used to screen for common autosomal aneuploidies in fetuses [3, 4]. The circulating cell-free DNA found in maternal plasma includes DNA of both maternal and fetal origins. Maternal circulating cell-free DNA originates from all maternal organs, including solid tumors, and mainly from the hematopoietic system. Fetal fraction (FF) is the ratio of cffDNA to all circulating cell-free DNA in the maternal plasma (Figure 1). Substantial research on the FF has been performed to date, but it is relatively scattered
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