Progress in non-invasive prenatal testing failure due to less cell-free fetal DNA

Non-invasive prenatal testing (NIPT) has been extensively applied in fetal chromosomal aneuploidy screening with high sensitivity and specificity. The concentration of cell-free fetal DNA (cffDNA) is an important factor related to the accuracy of NIPT. When cffDNA concentration is lower than 4%, accurate results are often unavailable, resulting in failure of NIPT. The factors influencing cffDNA concentration in maternal blood were reviewed and it was found that the concentration of cffDNA was positively correlated with the gestational week at the time of sampling, but negatively correlated with the maternal weight/body mass index. Moreover, gestational complications (such as preeclampsia and polycystic ovary syndrome), maternal age, results of serological screening for Down's syndrome in second trimester, fetal chromosomal karyotype and nuchal translucency thickness were also potential influencing factors. Analysis of the influencing factors of cffDNA concentration helps to improve the NIPT specifications, which is significant for prenatal genetic counselling. Key words: Aneuploidy; Prenatal diagnosis; Cell-free system; DNA; Fetus