Frontomaxillary facial angle in chromosomally normal Thai foetuses at 11 to 13 weeks 6 days’ gestation

Abstract

Frontomaxillary facial (FMF) angle is the angle between upper part of the anterior end of the maxillary bone and the line along the frontal bone in the midfacial profile view. Based on several previous studies, FMF angle can be useful in screening Down syndrome foetuses, in which FMF angle is significantly larger than that in euploid foetuses. However, racial factors can influence the FMF angle as seen in the different normal ranges among ethnicities. Therefore, before the clinical application of the FMF angle, a reference range for its own population should firstly be developed. In this study, a Thai reference range of FMF angle has been established. The mean FMF angle in euploid foetuses with a 60-mm crown–rump length (CRL) was 81.07°, with 0.23° increase for each mm increase in CRL, consistent with those observed in Caucasian and Chinese populations. The measurement of FMF angle has good reproducibility.

Keywords::

• Down syndrome
• frontomaxillary facial angle
• first trimester
• two-dimensional ultrasound (2D)
• screening

Acknowledgements

We wish to thank Dr. Alan Geater and Miss Walailuk Jitpiboon, Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, for statistical analysis..

Declaration of interest: This study was funded by Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand. We declare that we have no conflict of interest.