Diagnostic distinction between anencephaly and amnion rupture sequence based on skeletal analysis.

The axial skeletal development of eight second trimester aborted fetuses, clinically diagnosed as amnion rupture sequence with cranial involvement, was examined radiographically and histologically. Three of the eight fetuses showed axial skeletal malformation in the spine and the craniofacial skeleton corresponding to the malformations seen in anencephaly. These are vertebral body malformations, consisting of double corpora and of osseous malformations in the components of the cranial base, the corpus of the occipital bone, and the postsphenoid bone. These types of malformation, which have previously been described, are located along the original course of the notochord. The findings show that it is possible by means of radiography of the axial skeleton to distinguish between anencephalic fetuses which become secondarily involved in amnion rupture and fetuses which were initially normally developed. The method supplements detailed fetal examination and provides important information for genetic counselling.