Ultrasonography of the fetal nose, maxilla, mandible and forehead as markers for aneuploidy
Nowadays, the ‘combination test’ is offered to all pregnant women as a screening method for, among other conditions, Down syndrome. Despite this, only an estimated 30% of Dutch women actually apply for the test. As a consequence, a relatively large amount of the pregnant woman who present for the routine 20-weeks scan in the second trimester, has a fetus with an undetected chromosomal anomaly. Thus, tools and measurements that can be helpful to the ultrasonographer in affirming or weakening the suspicion of a chromosomal anomaly are important. In this thesis, several anatomical features in the fetal profile – the forehead, nose, maxilla and mandible – are described that can raise the suspicion of Down and Edwards syndrome, in case they are strongly abnormal. A group of fetuses with Down syndrome was measured retrospectively, of which 86% had a strongly abnormal ‘PT-NBL ratio’ (relation between the nasal bone and the skin anterior of the nose) and even 95% had an abnormal PT-NBL ratio and/or ‘PFSR’ (relation between the jaws and skin anterior of the nose). In the group of fetuses with Edwards syndrome, 88% had an abnormal PT-NBL ratio. Measurement of the ‘fetal profile line’, to assess the position of the mandible opposed to the forehead, can potentially differentiate between Down and Edwards syndrome. The conclusion of this thesis is that using relatively simple measurements in the fetal profile during the 20-weeks scan, the suspicion of a chromosomal anomaly like Down and Edwards syndrome can be substantiated.