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Iliac wing angle as a marker for trisomy 21 in the second trimester
1Department of Obstetrics and Gynecology, Oakwood Hospital and Medical Center, Dearborn, Michigan, USA.
Obstetrics and Gynecology
|May 1, 1997
Summary
The fetal iliac wing angle is a useful marker for detecting Down syndrome (trisomy 21) in pregnancy. Fetuses with trisomy 21 show a significantly greater iliac wing angle, aiding in antenatal screening.
Area of Science:
- Prenatal Diagnosis
- Fetal Medicine
- Genetics
Background:
- Second-trimester ultrasound is crucial for prenatal screening.
- Accurate detection of fetal aneuploidies like trisomy 21 is essential.
Purpose of the Study:
- To evaluate the efficacy of the fetal iliac wing angle in detecting trisomy 21 during the second trimester.
- To establish the diagnostic performance of this sonographic marker.
Main Methods:
- Ultrasonographic measurement of the iliac wing angle in 377 singleton fetuses.
- Karyotyping for trisomy 21 diagnosis.
- Calculation of sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV).
- Receiver operating characteristic (ROC) curve analysis to determine the optimal cutoff angle.
Main Results:
- Fetuses with trisomy 21 exhibited a significantly larger mean iliac wing angle (98.5°) compared to normal fetuses (68.2°).
- An ROC-derived cutoff of 90° demonstrated 90.9% sensitivity and 94.5% specificity for trisomy 21 detection.
- The NPV was 99.7%, while the PPV was 33.3% in this study population.
Conclusions:
- The fetal iliac wing angle is significantly greater in fetuses with trisomy 21.
- This sonographic measurement serves as a valuable marker for antenatal screening of trisomy 21, particularly in high-risk populations.