title: Maxilla-nasion-mandible (MNM) angle: an indicator to assess fetal facial profile in first-trimester of pregnancy.
abstract: OBJECTIVE
  The aim of this study was to observe whether there existed significant differences in the maxilla-nasion-mandible angle (MNM) between the first- and second-trimester of pregnancy, and to observe its predictive values for trisomy 18.
  
  
  METHODS
  Two experienced ultrasonologists used 2D and 3D ultrasound imaging techniques to obtain the facial sagittal sections of fetuses in the first-trimester of pregnancy (crown-rump length 45-84 mm), respectively, so as to measure MNM.
  
  
  RESULTS
  MNM could be measured in 91 % of normal fetuses, and the measurement differences by different operators in different groups were <1.1°; average MNM was 11.0°, and no significant change was observed in different gestational ages (P = 0.15). The average of MNMs in fetuses with trisomy 18 was 16.6°, which were all higher than the 95th percentile of normal measurement data. The sensitivity and specificity of increased MNM on the abnormal detection of trisomy 18 were 54.7 and 97.4 %, respectively.
  
  
  CONCLUSIONS
  The feasibility and reproducibility of measuring MNM in early pregnancy were good. MNM had certain suggestive roles for aneusomic chromosomal abnormalities, especially for fetuses with trisomy 18.
authors: Department of Ultrasound, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, 250014 Shandong China.
authors: Wei
authors: W
authors: Liu
authors: Department of Ultrasound, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, 250014 Shandong China.
authors: Suhui
authors: S
authors: Qu
authors: Department of Surgery, The First People's Hospital of Jinan City, Jinan, 250011 Shandong China.
authors: Mujun
authors: M
authors: Wang
authors: Department of Clinical Laboratory, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, 250014 Shandong China.
authors: Wanju
authors: W
authors: Xu
authors: Department of Ultrasound, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, 250014 Shandong China.
authors: Guangying
authors: G
authors: Zhang
authors: Department of Medicine Imaging, Shandong Provincial Qianfoshan Hospital, Shandong University, No. 16766 Jingshi Road, Jinan, 250014 Shandong China.
authors: Chengqi
authors: C
authors: Zhang
keywords: Aneuploid; Chromosome; MNM; Micromandible; Trisomy 18