We examined the axial skeleton in 15 human triploid fetuses (10 with XXX and 5 with XXY sex chromosomes). All fetuses 14-29 weeks of gestational age (GA), underwent wholebody radiography, permitting analysis of the nasal bone and the spine. From 9 of these, detailed radiographs were taken of midsagittal blocks of the cranial base and the spine, permitting detailed analysis of the cranial base.
Nasal bone: Of 14 fetuses, where the nasal bone was seen on lateral projection, it appeared short in 10 cases.
Spine: The spine was normal in 7 of 15 fetuses; malformations occurred in 8. These were osseous fusions between 2 or more vertebral bodies, most frequently in the cervical and thoracic regions, and disproportions in the sizes of the cervical bodies. Fusions occurred in 5 cases alone, and in one case in combination with disproportions of vertebral size. Disproportions alone occurred in 2 cases.
Cranial base: Malformation of the basilar part of the occipital bone was found in 5 of the 9 fetuses investigated. Of 9 fetuses, bilateral ossification centers of the postsphenoid bone occurred in 7, and shell-like ossification centers in 2.
There was no difference in the type of malformations in the different axial fields related to genotype (XXX and XXY).
Conclusion: The most remarkable findings in the axial skeleton of triploid fetuses are vertebral fusions in 6 of 15 cases; clefts of vertebral bodies, previously reported as common findings in trisomy fetuses, are not demonstrated. Am. J. Med. Genet. 72:216-221, 1997.