Monosomy 21q: two cases of del(21q) and review of the literature.

We report on two cases of partial monosomy 21 and review cases with a partial or an apparently full monosomy 21. In situ hybridization and/or molecular studies appear to be necessary tools to study imbalance in such a small chromosome and to perform further genotype-phenotype correlations. The segregation mode in cases with a translocation is adjacent 1, adjacent 2, and 3:1 in about 1/4, 1/4 and 1/2 of the cases, respectively.

[Study of the choice between sampling of the chorionic villi and the amniotic fluid in prenatal diagnosis].

We are reporting the results of a 21-month study during which 653 couples were seen in consultation at the prenatal diagnostic center of the University Hospital in Amiens, referred by their physician. 171 patients presented a theoretical term under 11 weeks of amenorrhea, for whom the choice between chorionic villi biopsy or amniotic fluid tap was possible. The different situations and results are compared for each method.