Frontomaxillary facial angle at 11 + 0 to 13 + 6 weeks in Chinese population.

ABSTRACT

OBJECTIVES: To establish the normal range of frontomaxillary facial (FMF) angle in the first trimester in a Chinese population. METHODS: In a prospective study from March 2007 to June 2007, three-dimensional (3D) volumes of the fetal profile in the mid-sagittal plane were recorded from 129 Chinese pregnant women who were screened for trisomy 21 by the combination of fetal nuchal translucency (NT) thickness, maternal serum free ß-human chorionic gonadotropin (ß-hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11 to 13 + 6 weeks. 3D volumes were examined using multiplanar techniques. The FMF angle of each case was measured. The relationship between the measured FMF angle with the other parameter was also examined. RESULTS: The mean FMF angle decreased from 86.8 degree for a crown-rump length (CRL) of 45 mm to 76.0 degree for a CRL of 84 mm (FMF angle = 99.49 - 0.28 x CRL, r=0.377, p<0.0001). There was no significant association between the FMF angle with serum PAPP-A or ß-hCG. The mean (SD) difference between FMF angle derived from Chinese formula and that from the published Caucasian equation was 1.47 (0.61) (95% CI 1.37-1.58) (p<0.0001). CONCLUSIONS: In the first trimester, the FMF angle decreases with fetal CRL. There was similarity in the normal value of FMF angle between the Chinese and Caucasian populations.