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Correlation between nuchal thickness and abnormal karyotype in first trimester fetuses
B G Hewitt1, L de Crespigny, A J Sampson
1Ultrasound Department, Royal Women's Hospital, Melbourne, VIC.
The Medical Journal of Australia
|October 7, 1996
Summary
First trimester nuchal thickness ultrasound accurately predicts fetal aneuploidy risk. Measurements of 3 mm or more indicate increased risk, while 1-2 mm measurements effectively exclude trisomy 21.
Area of Science:
- Prenatal diagnosis
- Fetal medicine
- Genetics
Background:
- First trimester ultrasound screening is crucial for prenatal diagnosis.
- Nuchal thickness measurement is a key parameter in early fetal assessment.
Purpose of the Study:
- To assess the accuracy of first trimester ultrasound nuchal thickness measurements in predicting fetal karyotype abnormalities.
Main Methods:
- Prospective study involving ultrasound measurement of fetal nuchal thickness in women undergoing chorionic villus sampling (CVS).
- Analysis of karyotype results from 1312 fetuses, correlating with nuchal thickness measurements.
Main Results:
- Abnormal karyotypes were found in 3.1% of fetuses.
- A nuchal thickness of 3 mm or more was observed in 49% of fetuses with abnormal karyotypes.
- Nuchal thickness measurements of 1-2 mm demonstrated a 99.3% negative predictive value for excluding trisomy 21.
Conclusions:
- First trimester nuchal thickening is a significant indicator of aneuploidy risk in high-risk pregnancies.
- Ultrasound measurement of nuchal thickness is a valuable tool for prenatal risk assessment.