Three-dimensional (3D) ultrasound offers several options extending conventional two-dimensional scanning. Various imaging modes are available. Three perpendicular planes displayed simultaneously can be rotated and translated in order to obtain accurate sections and suitable views needed for diagnosis and geometric measurements. 3D ultrasound tomography combines the advantages of ultrasound, e.g. safety, simplicity of application and inexpensiveness, with the advantages of sequentially depictable sections in numerous rotatable and translatable sections. Surface rendering gives detailed plastic images if there are surrounding layers of different echogenicity allowing for the definition of a certain threshold. Transparent modes provide an imaging of structures with a higher echogenicity in the interior of the object. A combination of the two modes sequentially definable by the sonographer allows for the optimal viewing of structures. These imaging modes are innovative features which have to be evaluated for clinical applicability and usefulness. Digital documentation of whole volumes enables full evaluation without loss of information at a later point. 3D technology provides an enormous number of technical options which have to be evaluated for their diagnostic significance and limitations in obstetrics and gynaecology.

The number of fetuses in which nuchal translucency could be measured tended to be higher with three-dimensional ultrasound, although the difference was not statistically significant. The possibility of rotating a stored volume and inspecting it in three orthogonal planes makes three-dimensional ultrasound a useful tool for nuchal translucency measurements, especially in doubtful cases.

Peak aortic velocity, a noninvasive assessment of fetal anemia, may be used as an additional test for monitoring pregnancies complicated by rhesus isoimmunization. However, the limited predictive capacity hampers its clinical usefulness.

We describe the results of prenatal analyses and postnatal findings in a male fetus with a partial trisomy for the long arm and a small terminal monosomy for the short arm of chromosome 4 with the following karyotype: 46,XY,add(4)(p16.3).ish dup(4)(q26qter)(wcp4+, D4S2336x3,AFMb280xa5x2,4ptel-,WHCR-). G-banding did not identify the origin of the additional chromosomal segment, but this was achieved prenatally by application of RxFISH and whole chromosome painting probes. Subsequent FISH analysis with region-specific YAC clones was used to relate the phenotypic findings such as bilateral split hand formation, specific cardiac and kidney anomalies, microtia, and hypoplastic thorax more exactly to the partial trisomy of the segment 4q26-qter.

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