Sonographic measurement of the fetal iliac angle in trisomy 21, 18 and 13

Objective: To determine whether iliac wing angle measurement in second trimester fetuses is a useful sonographic marker for the detection of trisomy 21, 18 and 13. Methods: During the period between September 1998 and September 2001, 406 fetal iliac angle measurements were performed in women in the second trimester of their pregnancies. The iliac angle measurements in fetuses with trisomy 21 (n = 25), trisomy 18 (n = 10) and trisomy 13 (n = 5) were compared with iliac angle measurement in fetuses with normal karyotypes (n = 333). Results: The mean iliac wing angle in the fetuses with trisomy 21 was 92.67 and 79.35° and 74° in fetuses with trisomy 18 and 13 (the mean iliac wing angle in the healthy fetuses was 70.09°). Conclusion: The proven larger iliac wing angle in neonates with Down’s syndrome can be demonstrated sonographically during the pregnancy, especially during the second trimester, and may be useful in prenatal screening of trisomy 21. The sonographic measurement of the fetal iliac angle cannot be used as a marker for trisomy 18 and 13. We have shown that fetuses with trisomy 18 and 13, on average, have iliac angles only a few degrees larger than healthy fetuses.