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Down syndrome or Down's syndrome, [12] also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. [3] It is usually associated with developmental delays, mild to moderate intellectual disability , and characteristic physical features.
A guide to Down syndrome including symptoms and diagnosis of this genetic condition.
Signs and symptoms of pregnancy are common, benign conditions that result from the changes to the body that occur during pregnancy. Signs and symptoms of pregnancy typically change as pregnancy progresses, although several symptoms may be present throughout. Depending on severity, common symptoms in pregnancy can develop into complications. [1]
The pregnancy loss rate in pregnancies with confined placental mosaicism, diagnosed by chorionic villus sampling, is higher than among pregnancies without placental mosaicism. It may be that sometimes the presence of significant numbers of abnormal cells in the placenta interferes with proper placental function.
In fact, consider that Down syndrome affects about 1:400 pregnancies; if you screened 4000 pregnancies with a Quad test, there would probably be 10 Down syndrome pregnancies of which the Quad test, with its 80% sensitivity, would call 8 of them high-risk. The quad test would also tell 5% (~200) of the 3990 normal women that they are high-risk.
Research has found that there is a correlation between advanced paternal age and risk of birth defects such as limb anomalies, syndromes involving multiple systems, and Down syndrome. [74] [35] [93] Recent studies have concluded that 5-9% of Down syndrome cases are due to paternal effects, but these findings are controversial. [74] [75] [35] [94]
Nuchal scanning alone detects 62% of all Down syndrome (sensitivity) with a false positive rate of 5.0%; the combination with blood testing gives corresponding values of 73% and 4.7%. [ 12 ] In another study values of 79.6% and 2.7% for the combined screening were then improved with the addition of second trimester ultrasound scanning to 89.7% ...
The most common abnormality the test can screen is trisomy 21 (Down syndrome).In addition to Down syndrome, the triple and quadruple screens assess risk for fetal trisomy 18 also known as Edwards syndrome, open neural tube defects, and may also detect an increased risk of Turner syndrome, triploidy, trisomy 16 mosaicism, fetal death, Smith–Lemli–Opitz syndrome, and steroid sulfatase ...