Prenatal screening for Down syndrome first became available for expectant mothers with the advent, in the late 1960s, of a diagnostic test employing amniocentesis and fetal karyotyping. At the time, only one risk factor was considered—the age of the mother.
In the ensuing years, discoveries showing the correlation between over- and under-expression of specific biomarkers in the mother’s blood, such as alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), estriol, and inhibin A, led to new prenatal screening tests that could indicate the likelihood of not only Down syndrome but other potential birth defects.
While these tests are still widely used and continue to serve a valuable function in helping physicians screen high-risk patients for potential abnormalities, these screening tools also have a relatively high incidence of false positives and false negatives. Women with a normal pregnancy are often referred for unnecessary invasive procedures such as amniocentesis or chorionic villus sampling, both of which carry a risk of miscarriage.
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