Construction of fetal inferior facial angle and hemi-mandible length reference ranges at 18-21 weeks' gestation in an Australian population

Robert Qiu; Katie MacKinlay; Melissa Suen; Andrew McLennan

doi:10.1002/ajum.12066

Construction of fetal inferior facial angle and hemi-mandible length reference ranges at 18-21 weeks' gestation in an Australian population

Australas J Ultrasound Med. 2017 Oct 7;20(4):168-173. doi: 10.1002/ajum.12066. eCollection 2017 Nov.

Authors

Robert Qiu¹, Katie MacKinlay², Melissa Suen², Andrew McLennan^{1

2}

Affiliations

¹ Faculty of Medicine The University of Sydney Sydney New South Wales 2006 Australia.
² Sydney Ultrasound for Women Chatswood New South Wales 2067 Australia.

Abstract

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.

Keywords: fetus; inferior facial angle; mandible; micrognathia; prenatal diagnosis; sonography.