Assessment of the maxilla-mandible-nasion angle in normal and aneuploid foetuses in the first trimester of pregnancy.
PURPOSE
This retrospective study aims to determine whether the maxilla-mandible-nasion (MMN) angle can be reliably measured in the first trimester, to describe normal ranges, and to determine if significant changes occur in foetuses with aneuploidies.


METHODS
The MMN angle was measured in stored 2D-ultrasound images of 200 normal fetal profiles between 11+0 and 13+6 weeks of gestation. Each image was analyzed by two observers at two independent time points. Bland-Altmann analysis was performed to evaluate the reliability of the measurements. Additionally, the MMN angle was measured on sonograms from 140 aneuploid foetuses.


RESULTS
The mean MMN angle in normal foetuses from 11 to 14 weeks of gestation was 15.4°. Reliability of the measurement was high when repeatedly measured by the same observer (ICC = 0.92 and 0.82) and between two observers (ICC = 0.77 and 0.63). Average MMN values in foetuses with trisomy 21, 13, and Turner syndrome were significantly higher than those measured in normal foetuses. The highest differences were observed in foetuses with trisomy 13. Among those, 62% had an MMN angle above the 95th percentile and 92% above the normal mean.


CONCLUSION
The MMN angle can be reliably measured in early pregnancy and is abnormal in about 60% of foetuses with trisomy 13.
['Tekesin|Ismail|I|https://orcid.org/0000-0002-5591-522X', 'Graupner|Oliver|O|']
D000328:Adult D000782:Aneuploidy D001837:Body Weights and Measures D005260:Female D006801:Humans D008334:Mandible D008437:Maxilla D019767:Maxillofacial Abnormalities D009666:Nose D011247:Pregnancy D011261:Pregnancy Trimester, First D015203:Reproducibility of Results D012189:Retrospective Studies D016216:Ultrasonography, Prenatal
maxilla-mandible-nasion angle aneuploidy first trimester pregnancy prenatal diagnosis ultrasound