K.B. Swamy,2003Andhra Medical College, Visakhapatnam-(A.P)
The population risk for trisomy 21 is 1 in 700 births but some couples are at much higher risk owing to parental translocation or mosaicism. The report is on the first attempt to carry out preimplantation genetic diagnosis for two such couples using cleavage stage embryo biopsy and dual colour FISH analysis, Each couple underwent two treatment cycles.
Couple 1 (suspected gonadal mosaicism for trisomy 21) had two embryos normal for chromosome 21 transferred, but no pregnancy resulted; 64% (7/11) unfertilized oocytes/embryos showed chromosome 21 eneuploidy. Couple 2 (46, XX, t(6;21) (q13;q22.3) had a single embryo transferred resulting in a biochemical pregnancy; 91% (10/11) oocytes/embryos showed chromosome 21 imbalance, most resulting from 3 : 1 seggregation of this translocation at gametogenesis. The opportunity to test embryos before implantation enables the outcome of female meiosis to be studied for the first time and the recurrence risk for a Down syndrome pregnancy to be assessed.
Couple 1 (suspected gonadal mosaicism for trisomy 21) had two embryos normal for chromosome 21 transferred, but no pregnancy resulted; 64% (7/11) unfertilized oocytes/embryos showed chromosome 21 eneuploidy. Couple 2 (46, XX, t(6;21) (q13;q22.3) had a single embryo transferred resulting in a biochemical pregnancy; 91% (10/11) oocytes/embryos showed chromosome 21 imbalance, most resulting from 3 : 1 seggregation of this translocation at gametogenesis. The opportunity to test embryos before implantation enables the outcome of female meiosis to be studied for the first time and the recurrence risk for a Down syndrome pregnancy to be assessed.
