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Sonographic screening for fetal aneuploidy: first trimester.
1Center for Perinatal Studies, University of Washington Medical Center, Seattle, USA.
Summary
First-trimester screening for fetal Down syndrome using nuchal translucency and biochemical markers offers high detection rates. Combined screening improves accuracy, though implementation questions remain.
Area of Science:
- Prenatal Diagnosis
- Maternal-Fetal Medicine
- Genetics
Background:
- First-trimester screening for fetal aneuploidy is feasible using ultrasound and biochemical markers.
- Nuchal translucency (NT) is a key sonographic marker for fetal aneuploidy.
Purpose of the Study:
- To review the efficacy of nuchal translucency in screening for fetal aneuploidy, particularly Down syndrome (trisomy 21) and other anomalies.
- To summarize the use of first-trimester sonographic and biochemical markers for aneuploidy screening.
Main Methods:
- Literature review of studies on first-trimester screening for fetal aneuploidy.
- Inclusion of over 16 studies on nuchal translucency published since 1995.
Main Results:
- Nuchal translucency screening shows sensitivities of 70-80% for Down syndrome with a 5% false-positive rate.
- Maternal serum markers (free beta-hCG, PAPP-A) with maternal age yield ~60% detection for trisomy 21.
- Combined NT, biochemical markers, and maternal age achieve ~85% detection for trisomy 21 with a 5% false-positive rate.
- Increased NT is associated with other aneuploidies like trisomy 18, 13, and Turner syndrome.
Conclusions:
- First-trimester screening for fetal Down syndrome and aneuploidies shows promise.
- Further multicenter studies are needed to address implementation questions in the United States.