Morphology of the 45,X embryo: an embryoscopic study.

The morphology of monosomy X in embryos was documented by means of transcervical embryoscopy prior to evacuation in 24 cases of missed abortion. The embryos ranged in size from 13 mm to 26 mm CRL and were all developed beyond the sixth week of development. The embryonic phenotype varied from nearly normal to obviously abnormal with a combination of localized external developmental defects consisting of microcephaly, facial dysplasia, and retarded limb development. A single case of encephalocele was observed. The factors responsible for the wide range of developmental defects observed in monosomy X embryos are currently unknown. Transcervical embryoscopy can serve as a central component for further genetic studies elucidating these mechanisms which are needed for reaching a further understanding of the developmental effects of specific aneuploidy in human morphogenesis.