First trimester ultrasound screening for chromosomal anomalies: Fetal nasal bone evaluation and maxillary length measurement

New attempts are continuously made at improving the performance of first trimester ultrasound screening for Down syndrome by searching for additional features in Down individuals which could be used from early in pregnancy as ultrasound markers. Two new potential markers have been identified: the presence of nasal bone and the maxillary length. The first one seems to be promising, but its incorporation in screening programs may be hampered by the fact that NB measurement requires higher technical skills and a longer learning curve than NT measurement. Maxillary length measurement is easier, but in view of its correlation with NT measurements its additional value as marker for Down syndrome seems limited.