Embryo biopsy strategies for preimplantation diagnosis

To analyze different biopsy methods, embryo stages, and cellular masses that can be removed for preimplantation diagnosis of genetic diseases to find optimal biopsy conditions compatible with the subsequent development of the conceptus, the acquisition of intact viable blastomeres, and the reliability of the genetic analysis.

The most important published studies have been identified through a computerized bibliographical search (MEDLINE; Dialog, Palo Alto, CA).

Studies reporting different embryo biopsy methods practiced at different stages have been selected.

The analysis carried out in the current review shows, at the present time, the following: [1] the displacement and push methods may be more suitable than the stitch and pull and aspiration (puncturing the zona pellucida) approaches at cleavages stages; [2] the aspiration and stitch and pull procedures may assure higher success rates than the herniation procedure at the blastocyst stage; [3] the mechanical division method and the use of acid Tyrode's solution would not be advisable before the eight-cell stage; [4] human embryos at the two-cell and blastocyst stages may not be suitable for preimplantation diagnosis because of an excessive reduction of cellular mass at the two-cell stage and a low or zero pregnancy rate after transfer at the blastocyst stage; and [5] biopsy of a quarter of the embryonic cellular mass on day 2 after insemination may increase biochemical pregnancies if the cleavage rate is not preserved.

At the present time, biopsy of a quarter of the embryo on day 3 after insemination may be the most feasible approach for preimplantation diagnosis.