The anatomy and histology of XO human embryos and fetuses

Abstract Thirteen abortuses with a known chromosomal complement of 45 (XO) were collected. Of these, eight contained an embryo or fetus ranging in age from five weeks to four months. Various gross anatomical abnormalities were evident in the four larger specimens and these included horseshoe kidney, unicornate uterus, single umbilical artery and cystic hygroma. One specimen had bilateral cystic hygromata. In all specimens, the gross anatomical appearance of the gonad was normal and, when examined histologically, the presence of primordial germ cells could be demonstrated. Histological sections of the XO gonads were compared with sections of gonads from known XX specimens of similar ages. There was no significant difference between the XO and XX gonads up to the third intrauterine month. In the older fetuses there was a relative increase in the connective tissue of the XO gonad. The finding of germ cells in the gonads of the XO fetuses is in contrast to the findings in XO adults who usually do not have germ cells in the gonads.