Down Syndrome

Abstract: 
Downs syndrome is a syndrome of mental retardation accompanied by abnormal facial features, which results when a baby inherits troika copies of chromosome 21 instead of the normal two copies. This chromosome abnormality, c every(prenominal)ed trisomy 21, may be detect prior to birth by culturing some cells from the fetus and examining the chromosomes straight off (karyotyping). However, this test is time-consuming and costly, and is normally reserved only for women at the greatest risk. Generally, this risk is determined by the mothers be on; women everyplace 36 be considered to be at the highest risk. However, Downs syndrome is the most familiar of all chromosome abnormalities and affects about 1 in 700 births. Women over 36 account for only about 30 percent of all Downs syndrome births and, at present, only about 15 percent of the cases of Downs syndrome are find before birth. It would be very valuable, therefore, to develop a screening method that would result in the prenatal perception of many fetuses with Downs syndrome without excessive cost. In a review of 3,436 pregnancies, 5 percent were karyotyped because of the mothers age and genetic history.



A total of viii affected fetuses were identified; the total may be considered 11, if three cases born shortly after the close of the study point in time are also considered. Only one of the affected fetuses was detected by conventional screening procedures. However, a new particularise of risk factors was designed that included the measurement of alpha fetoprotein and chorionic gonadotrophin in the mothers blood. The acceptable ranges were defined so that the number of karyotypes that would be recommended on the basis of these risk factors would be 5 percent, about the same as when maternal age is used as the predominant risk factor. Using these criteria, 8 of the 11 affected pregnancies would have been recommended for karyotyping, which would have yielded a espial rate of 73 percent. The adoption of this method of using risk...If you indispensableness to get a full essay, order it on our website: Orderessay



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