![]() ![]() The approximately 5% that survive for a year or longer after birth are usually severely mentally retarded and can have other serious medical problems. Many fetuses with Trisomy 18 are spontaneously lost during pregnancy or at birth. Trisomy 18 is a genetic abnormality specifically caused by an extra chromosome number 18. The chances of having a baby with Down syndrome increase with the mother’s age, but in general, about one in 700 babies are born with Down syndrome. The degree of severity of the abnormalities can vary between affected individuals. Individuals with Down syndrome are mentally retarded and can have serious medical problems such as heart defects. Fetuses with Down syndrome are spontaneously lost at a greater rate than unaffected fetuses during pregnancy. With recent attention to the importance of folic acid supplementation, there have been significant decreases in the prevalence of OSB-affected pregnancies.ĭown Syndrome is a genetic abnormality specifically caused by an extra chromosome number 21. Neural tube defects occur more often in individuals with previously affected children or with relatives who have had affected children. Only neural tube defects not covered by skin (open spinal bifida - OSB) are detected by this screening method. spina bifida) may result in handicaps that range from mild to ones as serious as paralysis or mental retardation. Neural Tube Defects are openings in the brain or spinal cord that occur early in fetal development. The three most common types of birth defects that may be detected by screening methods described in this review are neural tube defects, Down syndrome and Trisomy 18. By doing so, its total detection of Down syndrome risk is as good as the 1st Trimester Screen or the Full Integrated Screen (detects 86% of Down syndrome cases), and about 60% of the Down syndrome cases will be picked up during the first trimester. Sequential screening, however, provides information as early as the first trimester to the small number of women with very high risks (1:25 or greater) of carrying a fetus affected with Down syndrome. ![]() Sequential Integrated Screening offers a lower level of false positive tests than either the QUAD test or the First Trimester Screen, but slightly higher than the Full Integrated Screen. In this review, I present background information on prenatal screening and the most recent addition to the testing-Sequential Integrated Screening, and put its use in perspective of other available tests. Today, several options are available for prenatal screening. New Concepts in Prenatal Testing: Sequential Integrated Screening ![]()
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