Objective: To investigate the use of the retronasal triangle (RNT) for identification of orofacial cleft (OC) in the first trimester and the clinical application of three-dimensional (3D) ultrasound techniques for confirming the diagnosis of OC. Methods: A total of 5,054 women with singleton pregnancies underwent first-trimester screening for Down syndrome at 11-13+6 weeks. The RNT was scanned in each fetus, and 3D volumetric images of cases with abnormal or indeterminate RNT were obtained. Results: Satisfactory images were obtained from all cases. Seven cases (1.4‰) of abnormal RNT were diagnosed as OC in the first trimester, which were confirmed at a 16 weeks scan or at a postmortem examination. One case that was considered a normal RNT was diagnosed with OC at 22+2 weeks and after term delivery. Six cases of indeterminate RNT were diagnosed as normal by 3D ultrasound. Identification of OC by visualization of the RNT in the first trimester had a sensitivity of 87.5% and a specificity of 99.9%. Conclusion: The RNT is an important sonographic landmark that has a high sensitivity and specificity for the detection of OC in the first trimester. 3D ultrasound is an important tool that aids in confirming diagnosis of OC in the first and second trimesters.
P06.21: Visualization of the normal and cleft fetal palate at the time of the first trimester screening using three-dimensional extended imaging
