Will preimplantation genetic diagnosis assist patients with a poor prognosis to achieve pregnancy?

PGD (preimplantation genetic diagnosis) of aneuploidy for chromosomes X, Y, 13, 18 and 21 was carried out on 196 embryos from 36 infertile patients classified with a poor prognosis due to (i) maternal age, (ii) repeated in-vitro fertilization (IVF) failures and (iii) mosaic karyotype. The percentage of abnormal embryos was comparable in the three groups of patients: maternal age 63%, repeated IVF failure 57%, and mosaic karyotype 62%. The analysis of the overall data revealed an increased incidence of abnormal embryos in the older age categories (predominantly due to aneuploidy), even in embryos at the 7- to 8-cell stage. In addition, the percentage of chromosomally abnormal embryos was directly proportional to the number of IVF failures, where the increase in chromosomal abnormalities was not correlated to aneuploidy but to other aberrations such as mosaicism and polyploidy. Following PGD, 28 patients had at least one embryo transferred that appeared normal by fluorescent in-situ hybridization (FISH). Four clinical pregnancies resulted, with an implantation rate of 10% per normal embryo. In conclusion, the high rate of chromosomally abnormal embryos in poor prognosis patients may have been the cause of implantation failure in their previous IVF cycles. Therefore, the possibility of transferring embryos with a normal FISH complement could improve the chance of pregnancy in this category of patients.