Prenatal sex discernment The analysis of cffDNA from a sample of maternal plasma allows for prenatal sex discernment. Applications of prenatal sex discernment include: * Disease testing: Whether the sex of the fetus is male or<unk> e allows the determination of the risk of a particular X-linked recessive genetic disorder in a particular pregnancy, especially where the mother is a genetic carrier of the disorder. * Preparation, for any sex-dependent aspects of parenting. * Sex selection, which after preimplantation genetic diagnosis may be performed by selecting only embryos of the preferred sex, or, after post-implantation methods by performing sex-selective abortion depending on the test result and personal preference. In comparison to obstetric ultrasonography which is unreliable for sex determination in the first trimester and amniocentesis which carries a small risk of miscarriage, sampling of maternal plasma for analysis of cffDNA is without risk. The main targets in the cffDNA analysis are the gene responsible for the sex-determining region Y protein (SRY) on the Y chromosome and the DYS14 sequence. Congenital adrenal hyperplasia In congenital adrenal hyperplasia, the adrenal cortex lacks appropriate corticosteroid synthesis, leading to excess adrenal androgens and affects<unk> e fetuses. There is an external masculinization of the genitalia in the<unk> e fetuses. Mothers of at risk fetuses are given dexamethasone at 6 weeks gestation to suppress pituitary gland release of androgens. If analysis of cffDNA obtained from a sample of maternal plasma lacks genetic markers found only on the Y chromosome, it is suggestive of a<unk> e fetus. However, it might also indicate a failure of the analysis itself ( a false negative result). Paternal genetic polymorphisms and sex-independent markers may be used to detect cffDNA. A high degree of heterozygosity of these markers must be present for this application. Paternity testing Prenatal DNA paternity testing is commercially available. The test can be performed at nine weeks gestation. Single gene disorders Autosomal dominant and recessive single gene disorders which have been diagnosed prenatally by analysing paternally inherited DNA include cystic fibrosis, beta thalassemia, sickle<unk>  anemia, spinal muscular atrophy, and myotonic dystrophy. Prenatal diagnosis of single gene disorders which are due to an autosomal recessive mutation, a maternally inherited autosomal dominant mutation or large sequence mutations that include duplication, expansion or insertion of DNA sequences is more difficult. In cffDNA, fragments of 200 300 bp length involved in single gene disorders are more difficult to detect. For example, the autosomal dominant condition, achondroplasia is caused by the FGFR3 gene point mutation. In two pregnancies with a fetus with achondroplasia was found a paternally inherited G1138A mutation from cffDNA from a maternal plasma sample in one and a G1138A de novo mutation from the other. In studies of the genetics of Huntington's chorea using qRT-PCR of cffDNA from maternal plasma samples, CAG repeats have been detected at normal levels (17, 20 and 24). cffDNA may also be used to diagnose single gene disorders. Developments in laboratory processes using cffDNA may allow prenatal diagnosis of aneuploidies such as trisomy 21 (Down's syndrome) in the fetus. Hemolytic disease of the fetus and newborn Incompatibility of<unk>  and maternal RhD antigens is the main cause of Hemolytic disease of the newborn. Approximately 15 percent of Caucasian women, 3 to 5 percent of black Africa women and less than 3 percent of Asian women are RhD negative. Accurate prenatal diagnosis is important because the disease can be<unk>  to the newborn and because treatment including intramuscular immunoglobulin (Anti-D) or intravenous immunoglobulin can be administered to mothers at risk. PCR to detect RHD (gene) gene exons 5 and 7 from cffDNA obtained from maternal plasma between 9 and 13 weeks gestation gives a high degree of specificity, sensitivity and diagnostic accuracy (>90 percent) when compared to RhD determination from newborn cord blood serum. Similar results were obtained targeting exons 7 and 10. Droplet digital PCR in<unk>  RhD determination was comparable to a routine real-time PCR technique. Routine determination of<unk>  RhD status from cffDNA in maternal serum allows early management of at risk pregnancies while decreasing unnecessary use of Anti-D by over 25 percent. Aneuploidy ;Sex chromosomes Analysis of maternal serum cffDNA by high-throughput sequencing can detect common<unk>  sex chromosome aneuploidies such as Turner's syndrome, Klinefelter's syndrome and triple X syndrome but the procedure's positive predictive value is low. ;Trisomy 21<unk>  trisomy of chromosome 21 is the cause of Down's syndrome. This trisomy can be detected by analysis of cffDNA from maternal blood by massively parallel shotgun sequencing (MPSS). Another technique is digital analysis of selected regions (DANSR). Such tests show a sensitivity of about 99% and a specificity of more than 99.9%. Therefore, they cannot be regarded as diagnostic procedures but may be used to confirm a positive maternal screening test such as a first trimester screening or ultrasound markers of the condition. ;Trisomy 13 and 18 Analysis of cffDNA from maternal plasma with MPSS looking for trisomy 13 or 18 is possible Factors limiting sensitivity and specificity include the levels of cffDNA in the maternal plasma; maternal chromosomes may have mosaicism. A number of<unk>  nucleic acid molecules derived from aneuploid chromosomes can be detected including SERPINEB2 mRNA, clad B, hypomethylated SERPINB5 from chromosome 18, placenta-specific 4 (PLAC4), hypermethylated holocarboxylase synthetase (HLCS) and c21orf105 mRNA from chromosome 12. With complete trisomy, the mRNA alleles in maternal plasma isn't the normal 1:1 ratio, but is in fact 2:1. Allelic ratios determined by epigenetic markers can also be used to detect the complete trisomies. Massive parallel sequencing and digital PCR for<unk>  aneuploidy detection can be used without restriction to<unk> -specific nucleic acid molecules. (MPSS) is estimated to have a sensitivity of between 96 and 100%, and a specificity between 94 and 100% for detecting Down syndrome. It can be performed at 10 weeks of gestational age. One study in the United States estimated a false positive rate of 0.3% and a positive predictive value of 80% when using cffDNA to detect Down syndrome. Preeclampsia Preeclampsia is a complex condition of pregnancy involving hypertension and proteinuria usually after 20 weeks gestation. It is associated with poor cytotrophoblastic invasion of the myometrium. Onset of the condition between 20 and 34 weeks gestation, is considered "early". Maternal plasma samples in pregnancies complicated by preeclampsia have significantly higher levels of cffDNA that those in normal pregnancies. This holds true for early onset preeclampsia.
Cell-free fetal DNA
Human milk microbiome
Circulating mitochondrial DNA
Genetically modified virus
Reporter virus particles
Placental microbiome
Immature ovum
Products of conception