Authors' recommendations: It is estimated that aneuploidy (i.e., having missing or extra chromosomes) is the cause of 6% to 11% of stillbirths and neonatal deaths, and that up to 0.65% of newborns may experience significant medical problems as a result of this type of chromosome abnormality. In humans, each cell is expected to have 23 pairs of chromosomes, including 2 X chromosomes in females (represented as 46,XX) and an X and a Y chromosome in males (represented as 46,XY). Among live-born infants with an aneuploidy, most carry an extra chromosome, which is known as a trisomy (having 3 copies of a chromosome instead of the expected 2). The most common of these conditions is trisomy 21 (T21, or Down syndrome), which results from the presence of an extra copy of chromosome 21. Other common conditions include trisomy 18 (T18, or Edwards syndrome), trisomy 13 (T13, or Patau syndrome), Klinefelter syndrome (47,XXY), triple X syndrome (47,XXX), and 47,XYY syndrome. However, the loss of a single chromosome (monosomy) is also possible, as can be seen in those with Turner syndrome (45,X). An increased risk of having a child with an aneuploidy is the most common reason couples are referred for prenatal testing. The prenatal diagnosis of chromosome abnormalities requires an analysis of fetal cells obtained by either chorionic villus sampling (CVS) or amniocentesis, invasive procedures that are associated with a risk of fetal loss. Because of the risks associated with CVS and amniocentesis, most women choose to have a noninvasive screening test to better assess their personal risk before considering invasive testing options. Screening tests are designed to identify women who are more likely to have a child with T21, T18, or T13, but they cannot diagnose or exclude the possibility of a chromosome disorder. In addition, the detection rate for these tests typically ranges from 68% to 90%, with up to 5% of patients having a false-positive result and potentially unnecessary invasive diagnostic testing. Noninvasive prenatal testing (NIPT; also referred to as noninvasive prenatal screening [NIPS] and previously referred to as noninvasive prenatal diagnosis [NIPD]) is a new advanced screening test designed to detect the most common fetal aneuploidies in a noninvasive manner. Currently, there are 4 NIPT assays available in the United States. They are (in order of market entrance date): the MaterniT21 PLUS, the Verifi Prenatal Test, the Harmony Prenatal Test, and the Panorama Prenatal Test. These assays involve the analysis of cell-free fetal DNA (cffDNA) that is present in a mother's blood during pregnancy in order to detect aneuploidies involving specific chromosomes. They use recently developed molecular techniques, such as massively parallel sequencing (MPS; i.e., the sequence analysis of millions of DNA fragments at the same time), that allow for an evaluation of chromosome representation in the cell-free component of a blood sample (i.e., plasma). However, each NIPT assay is different with respect to its exact methodology and algorithms for data analysis. NIPT requires only a maternal blood sample, may be performed as early as at 9 to 10 weeks of gestation, and may test for aneuploidies involving chromosomes 21, 18, 13, and the sex chromosomes. The proposed advantages of NIPT are that the detection rate is much higher (approximately 99% for T21 and T18, and > 90% for T13) and the false-positive rate is much lower (< 1%), when compared with other screening options. Therefore, it is expected that using this test prior to CVS or amniocentesis will increase the overall detection of fetal aneuploidies, decrease the number of unnecessary invasive testing procedures performed, and decrease the number of procedure-related pregnancy losses.

Project Status: Completed

Year Published: 2013

URL for published report: The report may be purchased from: http://www.hayesinc.com/hayes/crd/?crd=15509

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: HAYES, Inc.

Contact Address: 157 S. Broad Street, Suite 200, Lansdale, PA 19446, USA. Tel: 215 855 0615; Fax: 215 855 5218

Contact Name: saleinfo@hayesinc.com

Contact Email: saleinfo@hayesinc.com

Copyright: 2013 Winifred S. Hayes, Inc