Objective assessment of the fetal facial profile at second and third trimester of pregnancy

Objective To investigate the intraobserver and interobserver reproducibility of a novel sonographic parameter named facial maxillary angle (FMA) and to establish nomograms of FMA, inferior facial angle (IFA), frontal nasal-mental angle (FNMA), maxilla-nasion-mandible angle (MNMA), and fetal profile line (FPL) in Chinese fetuses. Methods In this prospective cross-sectional study, FMA, IFA, FNMA, MNMA, and FPL were measured in 592 normal fetuses between 16 and 36 gestational weeks. FMA was measured twice by the same and another operator with a blinded method on the first 50 cases. The reference interval was defined as +/- 2SD. The efficacy of five sonographic markers was tested in 10 fetuses with micrognathia retrieved from the database of our unit. Results The intraclass correlation coefficient (95% CI) of intraobserver and interobserver reproducibility of FMA was 0.937 (0.890-0.964) and 0.891 (0.809-0.938), respectively. FMA, FNMA, and IFA increased slightly from 16 weeks till 28-31 weeks and decreased minimally thereafter. FMA and FNMA made correct diagnosis in all affected fetuses; MNMA and IFA identified nine and eight cases respectively, and FPL only detected five cases. Conclusion A fixed cutoff of 66 degrees for FMA and 136 degrees for FNMA may be adopted as simple screening criteria of micrognathia.