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Nuchal fold thickness is measured towards the end of the second trimester. As nuchal translucency size increases, the chances of a chromosomal abnormality and mortality increase; 65% of the largest translucencies (>6.5mm) are due to chromosomal abnormality, while fatality is 19% at this size. [2] A nuchal scan may also help confirm both the ...
Perhaps the most common such test uses a measurement of the nuchal translucency thickness ("NT-test", or "Nuchal Scan"). Although 91% of fetuses affected by Down syndrome exhibit this defect, 5% of fetuses flagged by the test do not have Down syndrome. Ultrasound may also detect fetal organ anomaly.
Screening tests can then include serum analyte screening or cell-free fetal DNA, and nuchal translucency ultrasound [NT], respectively. [60] It is important to note that screening tests are not diagnostic, and concerning screening results should be followed up with invasive diagnostic testing for a confirmed diagnosis.
This includes an association between high levels of abnormal cells in placental tissue and concerns with the growth of the baby. However, it is not accurate to use these associations to try to predict pregnancy outcome based on the percent of trisomic cells in a first trimester CVS result. [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 ...
[2] However, a flurry of independent studies in the late '80s and '90s affirmed the diagnostic value of fetal ultrasound, and the nuchal translucency scan (pictured), the first-trimester analog of the nuchal fold thickness test, is now a standard component of prenatal aneuploidy screening.
A systematic review published in 1998 showed that home pregnancy test kits, when used by experienced technicians, are almost as accurate as professional laboratory testing (97.4%). When used by consumers, however, the accuracy fell to 75%: the review authors noted that many users misunderstood or failed to follow the instructions included in ...
Other prenatal screening tests include serum integrated protein tests, cell free DNA blood tests to check for chromosomal abnormalities, and nuchal translucency ultrasounds. If their medical system is able to provide them, mothers can also undergo more invasive diagnostic tests such as an amniocentesis, or chorionic villous sampling to detect ...