Study on the applicability of frontomaxillary facial angle in the first-trimester trisomy 21 fetuses in Chinese population.

ABSTRACT

OBJECTIVE: To evaluate the measurement of frontomaxillary facial (FMF) angle at 11 weeks to 13 weeks, 6 days in a Chinese population and its applicability in the screening for fetal trisomy 21. METHOD: In a retrospective study, the stored images for the measurement of fetal nuchal translucency (NT) thickness in a Chinese population from August 2003 to March 2007 were reviewed for the comparison of the FMF angle between 22 trisomy 21 fetuses (study group) with 220 randomly selected normal fetuses with satisfactory images (control group). RESULTS: No association between FMF angle and NT, nasal bone length, or fetal heart rate was shown (P > 0.05). But the FMF angle was significantly greater in the trisomy 21 fetuses (89.7 vs 82.8, P < 0.001). The intraobserver and interobserver agreement were assessed in 9.5% (n = 21) normal cases. Mean (SD) differences of two observers were -0.83 (2.69) degrees (P > 0.05). For each observer, mean (SD) differences between the two paired measurements were -0.98 (3.11) degrees and 0.93 (1.80) degrees , respectively (P > 0.05). CONCLUSION: Our results indicated that measurement of the FMF angle in the first trimester can be incorporated into the screening of trisomy 21 in the Chinese population, and its application is not affected by intraobserver and interobserver variability.