Trisomy 18

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Edwards Syndrome, also known as Trisomy 18, is a genetic syndrome of severe to profound mental retardation. It is caused by the presence of an extra chromosome 18 in some or all of the cells in the body. Babies with this condition typically do not survive but for a few months after birth. About sixty percent of newborns with this condition die within the first week, and eighty percent do not survive through the first month. Trisomy 18 in a fetus or embryo is also a common cause of pregnancy loss.

Trisomy refers to a cell that contains three of the same chromosome, Trsiomy 18 then refers to three chromosomes of number 18. Trisomy 18 is the second most common condition of mental retardation seen in live-born babies. Trsiomy 21 (down syndrome) is the most common.

The majority of pregnancies in which the fetus or embryo has trisomy 18 will result in miscarriage or stillbirth. Some physical defects of the heart, skeleton, brain, kidneys, and body walls have a good chance of bein detected by prenatal ultrasound. Women carrying a fetus with Edwards Syndrome sometimes report that they feel little movement. Cesarean sections are more common due to abnormal fetal positon or fetal distress near term.

Of those babies with Edwards Syndrome that are live-born, two-thirds are delivered several weeks early or late. Another common effect is low birth weight. Newborns are frail, and tend to have a weak cry and difficulty feeding. Muscles may be poorly developed, and often become tight and contracted. Extra hair on the forehead and back is sometimes seen, as is loose, redundant skin.

Abnormalities of the lungs, kidneys, pancreas, and spleen are...
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