Clinical pregnancy following blastomere biopsy and PGD for a reciprocal translocation carrier: analysis of meiotic outcomes and embryo quality in twoIVF cycles

A couple Were referred for preimplantation genetic diagnosis (PGD) followin g diagnosis of a reciprocal translocation in the female partner: 46,XX,t(14 ;22)(q11.2;q13.3). PGD was carried out using fluorescence in situ hybridiza tion (FISH) with probes specific for the translocated and centric segments of chromosome 22. An initial cycle was unsuccessful, producing 11 embryos f or biopsy, only one of which, when followed up on day 4, yielded more than 10 nuclei (median 7.5, n = 10). In addition, five of the embryos showed mos aic or chaotic chromosome constitutions; some of these embryos had fragment ed or multilobed abnormal nuclei, hindering interpretation of the FISH sign als. The single embryo transferred did not result in a pregnancy. A second cycle, using a revised protocol, produced 10 embryos, three of which Were t ransferred, resulting in an ongoing singleton pregnancy. All the remaining embryos yielded 12 to 23 nuclei by day 3 (median 17, n = 7). Apart from som e tetraploid nuclei, only one embryo showed mosaicism. The significance of the changes in protocol leading to the successful outcome is discussed, and the pattern of meiotic segregation products is analysed and compared with other previous reports of reciprocal translocations. Copyright (C) 2000 Joh n Wiley & Sons, Ltd.