![]() ![]() In addition, the amount of circulating fetal DNA depends, besides the gestation period, on other factors, such as maternal diseases and body weight (Zhou et al., 2015 Vora et al., 2012), aneuploidies (Zhou et al., 2015) and twin pregnancies (Attilakos et al., 2011).Īnyway, the very low amount of circulating cell-free DNA in maternal plasma is a very crucial issue and specific and optimized techniques for cffDNA purification from maternal plasma, and very sensitive detection approaches are required. The proportion of circulating cffDNA grows by 0.1% every seven days between the 10th and 21st week of gestation, then increases faster after the 21st week, reaching almost 1% increment every week (Drury et al., 2016 Zhou et al., 2015). However, fetal DNA is present in maternal blood at very low concentrations increasing during the progression of pregnancy (Zhou et al., 2015). (Lo et al., 1997), through a simple PCR and the use of specific probes for the DYS14 gene, located in single copy on the Y chromosome, demonstrated the presence of fetal DNA in plasma samples of pregnant women bearing male fetuses.īetween 3 and 13% of the total circulating free DNA in the plasma of pregnant women is thought to be fetal DNA (Drury et al., 2016). The Y chromosome was the first marker developed for the detection of circulating cffDNA in maternal blood (Lo et al., 1997). NIPD is based on fetal DNA analysis starting from a simple peripheral blood sampling without disrupting or endangering the health of the unborn child and the pregnant woman, thus eliminating the risks associated with conventional invasive techniques withdrawal. (Lo et al., 1997) of circulating cell-freefetal DNA (cffDNA) in maternal plasma. Non-invasive prenatal diagnosis (NIPD) started after the discovery by Lo et al. While the fetal sex diagnosis could be obtained using invasive procedures such as amniocentesis and chorionic villus sampling, these procedures are associated with a 1% risk of miscarriage (Sillence et al., 2015). In particular, determination of fetal sex is especially useful in congenital adrenal hyperplasia, permitting the target therapy to female fetuses (New et al., 2014 Sillence et al., 2015). The ddPCR is a robust, efficient and reliable technology for the earliest possible fetal sex determination from maternal plasma.Ĭurrently more than 100 X-linked inherited human disorders have been identified, such as hemophilia, adrenal hypoplasia, muscular dystrophy (Becker, Duchenne and Emery-Dreifuss types), taking a relevant place in the genetic counseling (Germain, 2006). ![]() ResultsĪll maternal plasma samples were determined correctly for SRY gene target using ddPCR even at very early gestational age (prior to 7 weeks). We identified the fetal sex on cffDNA extracted from 29 maternal plasma samples at early gestational ages, several of them not suitable for qPCR determination, using ddPCR designed for SRY gene target. In this context we employed droplet digital PCR (ddPCR) in order to evaluate the earliest possible fetal sex determination from circulating DNA extracted from plasma of pregnant women at different gestational ages. However, the low amount of cffDNA relative to circulating maternal DNA requires highly sensitive molecular techniques in order to perform noninvasive prenatal diagnosis. Since the discovery of cell-free fetal DNA (cffDNA) in maternal plasma, noninvasive prenatal testing permits the early diagnosis of fetal sex through analysis of cffDNA. At first, this could be obtained through invasive procedures such as amniocentesis and chorionic villus sampling, having a 1% risk of miscarriage. Fetal sex determination is useful for families at risk of X-linked disorders, such as Duchenne muscular dystrophy, adrenal hypoplasia, hemophilia. ![]()
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