Chromosome microdeletion is an invisible threat to fetal health. Through karyotype analysis of amniotic fluid, common diseases with abnormal chromosome number, such as Down's disease, Turner's disease and Klinefeld's disease, can be detected, and the accuracy rate can reach over 99%. It is a mature prenatal chromosome diagnosis method, but the detection limit can only reach 5~ 10mb due to manual visual inspection. There are many diseases caused by the deletion of chromosome micro-fragments smaller than or between 3 and 5 MB, such as chubby Willie's disease, angel syndrome, Degeorge's syndrome and so on. Traditional chromosome analysis can not be accurately detected. Diseases caused by the deletion/duplication of these chromosome fragments will lead to gene deletion and cause fetal developmental abnormalities such as mental retardation, abnormal facial features, developmental defects, developmental retardation and other clinical manifestations. At present, more than 370 species are known, and the comprehensive incidence rate can reach about11000, but the traditional amniotic fluid chromosome analysis can not be effectively detected. Therefore, many obstetricians and gynecologists will advise pregnant women to use microarray-based comparative genomic hybridization to collect amniotic fluid at the same time during pregnancy 16- 18 weeks; ACGH) analysis to prevent fetal pathogenic chromosome microdeletions. If pregnant women are unwilling or unsuitable to take amniotic fluid, they can also screen the most common 20 kinds of chromosomal abnormalities and fragment deletion through the non-invasive fetal chromosome gene detection (NIFTY PLUS), which can greatly reduce the risk of accidentally giving birth to a fetus with chromosomal abnormalities.
Compared with traditional karyotype analysis, amniotic fluid analysis and amniotic fluid chromosome gene chip can greatly improve the resolution of chromosome gene chip to 10~50kb, and can detect more than 370 diseases caused by chromosome microdeletions. It is a very reliable chromosome examination method to minimize the risk of human error through chip scanning and computer data analysis. In 20 13, the American College of Obstetrics and Gynecology issued a proposal, amniotic fluid chromosome gene chip (comparative genomics hybridization based on microarray; ACGH) is listed as a method of clinical prenatal diagnosis. According to the research of American College of Obstetrics and Gynecology, if the chromosome gene chip is detected at the same time under the normal ultrasonic examination, the abnormal detection rate can be improved by about 65438 0.7%. A study in the New England Journal of Medicine pointed out that the fetus was abnormal after receiving high-level ultrasound examination, and the chromosome gene chip could find 6% more chromosomal abnormalities than the traditional chromosome examination. In addition, when pregnant women have unexplained abortion, compared with the general traditional chromosome examination, chromosome gene chip detection can detect 13% more chromosome abnormalities, which is helpful to find out the causes of habitual abortion. However, some special cases of chromosome translocation, inversion and chimerism still rely on traditional chromosome analysis to judge. Amniotic fluid chromosome analysis and amniotic fluid chromosome gene chip cannot replace each other. Usually, doctors will advise pregnant women to consider extracting amniotic fluid and accepting amniotic fluid chromosome gene chip detection, which sets up a double guarantee for the baby's health.
Figure/A large amniotic fluid chromosome gene chip detection unit in Taiwan Province Province
The quality of prenatal chromosome diagnosis and genetic counseling is the most important. Before extracting amniotic fluid for amniotic fluid chromosome gene chip detection, pregnant women must know whether the detection unit cooperated by the maternity inspection institute is a clinical cytogenetics laboratory that has passed the examination of the national medical service system and meets the inspection quality accreditation standard of * * * *, and the detection quality can be guaranteed by law. Although there are more than 370 kinds of chromosome microdeletions/repetitions that cause diseases, the detection of other chromosome deletions/repetitions does not mean that the fetus will have developmental defects or diseases, and the results must be reviewed by genetic consultants, which is of substantial significance to pregnant women and fetuses.
References: 1. Comparison of chromosome microarray and karyotype analysis in prenatal diagnosis. British medical journal 2012; 367: 2175-2184.201221February 6th. ACOG· Mitter's opinion No.5812013. 3. Chromosome microarray analysis (CMA) provides more information than routine karyotype analysis in the diagnosis of chromosomal abnormalities in abortion: a systematic review and meta-analysis. BJOG。 20 14 January; 121(1):11-21.4. List of clinical cytogenetic testing institutions recognized by the National Health Administration of the Ministry of Health and Welfare: ntuh.gov/gene/link/Pages/cytolist1.aspx.
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