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Preimplantation genetic diagnosis: polar body or embryo biopsy, which technique is more effective?

O-278 Preimplantation genetic diagnosis: polar body or embryo biopsy, which technique is more effective?

  1. M.G. Minasi1,
  2. A. Ruberti1,
  3. P. Rubino1,
  4. E. Iammarrone2,
  5. A. Biricick2,
  6. D. Zavaglia1,
  7. A. Nuccitelli2,
  8. A. Colasante1,
  9. F. Fiorentino2 and

10. E. Greco1

+ Author Affiliations

  1. 1European Hospital, Reproductive Medicine, Rome, Italy
  2. 2Genoma, Molecular Genetics Laboratory, Rome, Italy

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Abstract

Introduction: Preimplantation genetic diagnosis (PGD) allows the diagnosis of genetic disorders before embryo transfer. This procedure can be performed at different stages: oocyte (Pre-Conception Genetic Diagnosis; PCGD), embryo or blastocyst. Embryo biopsy is the most commonly performed. However, polar body (PB) biopsy permits to overcome the ethical issues concerning embryo diagnosis. In Italy, under the Italian 40/2004 law, from March 2004 to May 2009, embryo manipulation was not allowed and only PB biopsies were performed. From May 2009, when the Constitutional Court allowed the evaluation of health status of the embryo, embryos biopsies are again possible. The aim of this retrospective study is to evaluate the efficacy of the two procedures in terms of numbers of embryos obtained for transfer and take-home-baby rate.

Material and Methods: From December 2007 to January 2009, 21 cycles (mean female age 34.8 ± 3.6) of PCGD were performed. Oocytes were denuded at 36 hours after hCG administration and all mature oocytes were biopsied. Unaffected oocytes were inseminated at 43-45 hours from hCG administration and embryos were transferred on day-3. From October 2009 to December 2010, 55 cycles of PGD were performed (mean female age 33.3 ± 4.3, NS). Oocytes were denuded at 39-40 hours after hCG administration and MII were immediately inseminated. On day-3, one blastomere was removed from embryos ≥5 cells. Transferable embryos were replaced on day-4/5. Both for oocytes and embryos, Zona Pellucida was opened by a laser-dissection, PB/blastomere were removed using a micro-pipette and sent for genetic analysis. Statistical analysis was performed using Fisher’s exact test at the level of P < 0.05.

Results: In PCGD-group, 194 oocytes were biopsied: 42 were normal, 80 affected, 61 recombinant (no conclusive diagnosis) and 11 without genetic result. All the 42 usable oocytes were injected, 31 fertilized (73.8%) and 26 embryos were obtained. Twenty-six embryos were transferred in 16 patients (1.6/cycle): 3 had + βhCG (18.8%), 3 were clinical pregnancy (18.8%), 3 embryos implanted (11.5%), 3 delivered (18.8%) and 3 healthy babies were born. In embryo-biopsy group, 511 oocytes were available. All of them were injected, 391 fertilized (76.5%, NS) and 380 embryos were obtained. On day-3, 356 embryos were biopsied. Genetic results were: 161 normal/carrier, 129 affected and 66 no results embryos. On day 4/5, 96 embryos were transferred in 50 patients (1.9/cycle): 24 had β + test (48.0%, NS), 20 were clinical pregnancy (40.0%, NS), 31 embryos implanted (32.3%, p < 0.05), 19 delivered (38.0%, NS) and 26 healthy babies born. In addition, 41 normal/carrier embryos in 18 cycles were cryopreserved. Both number of transferable embryos (p < 0.0001) and number of babies born (p < 0.05) in respect to the number of available oocytes was higher in embryo-PGD group (161 embryos and 26 newborn/511 oocytes) than in PCGD-group (26 embryos and 3 newborns/194 oocytes).

Conclusion: In conclusion, embryo PGD seems to have a better performance than PCGD. One limitation of this procedure is that the paternal alleles cannot be analyzed. Moreover, recombinant oocytes have a non conclusive diagnosis and must be discarded, in order to avoid the risk of using an affected oocyte. Finally, not all healthy oocytes fertilize, leading to a further loss of transferable embryos. We found a higher number of embryos and newborns in respect to available oocytes, when embryo biopsy was performed. In addition, implantation rate was higher after PGD and there are still some cryopreserved embryos which could lead to an increasing cumulative pregnancy rate. In recent years, blastocyst biopsy appeared as a good alternative to embryos PGD. Currently in our centre a prospective study on efficacy of trophectoderm in respect to blastomere biopsy is in progress.