First trimester sonographic findings of trisomy 21, 18, and 13

Image A: Sagittal view of a fetus at 12 weeks demonstrating enlarged nuchal translucency between caliper marks. The nasal bone is present. The fetal karyotype was trisomy 21.
Image B: Axial scan through the fetal chest demonstrating the 4-chamber view of the heart with a large atrioventricular canal (arrow). The fetal karyotype was trisomy 21.
Image C: Sagittal view of an 11 week fetus with a large liver containing omphalocele (short arrow). The fetal karyotype was trisomy 18.
Image D: Sagittal view of a 13 week fetus with megacystis (dashed arrow). The fetal karyotype was trisomy 18.
Image E: Axial scan through the fetal head at 14 weeks showing a monoventricle (thick arrow) characteristic of alobar holoprosencephaly and distortion of the remaining intracranial anatomy. The fetal karyotype was trisomy 13.
Image F: Sagittal image of a fetus at 12 weeks demonstrating an abnormal profile contour and micrognathia (arrowhead) as well as an enlarged nuchal translucency (*). The fetal karyotype was trisomy 13.