[Studies on phenotype, development, and viability of human spontaneous abortuses with acrocentric trisomies and polyploidies: with reference to the relationship of the viability to the origin of extrachromosomes (author's transl)]

Abstract

The specimens to be presented consist of 65 trisomics and 37 polyploids which were obtained from a cytogenetic survey of human spontaneous abortion with various chromosome banding techniques. The phenotype of the 102 abortuses was analysed macroscopically before and after fixation of the tissues. The developmental age was estimated with the crown-rump measurement and from stage of Streeter's horizon on embryos and fetuses, or from the size of the placenta when an embryo was lost. The degree of phenotypic abnormality and the developmental age were used on determining the viability of abortuses. This viability was examined in each type of chromosomal anomlies. Three of 4 13-trisomics and all of 4 21-trisomics showed normal phenotype and advanced development, while most of 14-trisomics, 15-trisomics and 22-trisomics had the various severe phenotypic anomalies such as blighted ovum and disorganized embryo, and less developed. These findings suggest that abortuses with the chromosomal anomalies which can be found in the newborns longer survive than those with other anomalies. In other words, these anomalies have a better viability among abortuses. Eleven trisomics and 11 polyploids were ascertained for the origin of extra chromosomes by sequential QFQ- and RFA-banding. Of 7 abortuses with trisomy 21 studied, 4 originated at the maternal meiotic non-disjunction and none was of paternal origin. On the other hand, several published studies have shown that the paternal origin is not uncommon in Down children. Therefore, as far as trisomy 21 is concerned, it is concluded that the trisomy 21 of paternal origin has much better survival rate than that of maternal origin. In triploidy, the present study could not define the relationship between the viability and the origin, since 9 of 10 abortuses studied and all of 4 triploid newborns so far reported are of paternal origin.