RESUMO
OBJECTIVE: The aim of this pilot study was to provide modern reference intervals for both inferior facial angle and hemi-mandible length in fetuses of 18-21 weeks' gestation. METHODS: Prospectively, 296 apparently normal fetuses were sonographically assessed at 18-21 weeks' gestation. Inferior facial angle and hemi-mandible length were measured and parametrically analysed with respect to gestational age. Regression models were derived for each parameter and compared with models of previous studies. RESULTS: The mean inferior facial angle remained constant over the studied gestational age range at 63.9°, with 5th and 95th percentiles of 56.6° and 73.4°, respectively. Hemi-mandible length was found to be positively correlated with gestational age over the studied range, and the mean value is described by the equation 40.89 mm - (6327.495 × GA-2) with a standard deviation of 1.231 mm. CONCLUSION: Modern reference intervals for inferior facial angle and hemi-mandible length were defined within this pilot study. These reference intervals will aid in improving accuracy diagnosing micrognathia and our ability to differentiate true micrognathia from retrognathia.
