EMBRYO BIOPSY STRATEGIES FOR PREIMPLANTATION DIAGNOSIS

Objective: To analyze different biopsy methods, embryo stages, and cel lular masses that can be removed for preimplantation diagnosis of gene tic diseases to find optimal biopsy conditions compatible with the sub sequent development of the conceptus, the acquisition of intact viable blastomeres, and the reliability of the genetic analysis. Data Identi fication: The most important published studies have been identified th rough a computerized bibliographical search (MEDLINE; Dialog, Palo Alt o, CA). Study Selection: Studies reporting different embryo biopsy met hods practiced at different stages have been selected. Results: The an alysis carried out in the current review shows, at the present time, t he following: [1] the displacement and push methods may be more suitab le than the stitch and pull and aspiration (puncturing the zona pelluc ida) approaches at cleavages stages; [2] the aspiration and stitch and pull procedures may assure higher success rates than the herniation p rocedure at the blastocyst stage; [3] the mechanical division method a nd the use of acid Tyrode's solution would not be advisable before the eight-cell stage; [41 human embryos at the two-cell and blastocyst st ages may not be suitable for preimplantation diagnosis because of an e xcessive reduction of cellular mass at the two-cell stage and a low or zero pregnancy rate after transfer at the blastocyst stage; and [5] b iopsy of a quarter of the embryonic cellular mass on day 2 after insem ination may increase biochemical pregnancies if the cleavage rate is n ot preserved. Conclusions: At the present time, biopsy of a quarter of the embryo on day 3 after insemination may be the most feasible appro ach for preimplantation diagnosis.