Removal of 2 cells from cleavage stage embryos is likely to reduce the efficacy of chromosomal tests that are used to enhance implantation rates.

OBJECTIVE: To evaluate whether differences in results between studies that involve preimplantation genetic diagnosis for chromosome testing are affected by technology, such as the number of cells to be biopsied or by differences in study design. DESIGN: Evaluation of studies of aneuploidy testing according to the use of probes, fixation technology, error determination, and number of cells per embryo analyzed. SETTING: Preimplantation genetic diagnosis laboratories. PATIENT(S): Patients in published studies who underwent preimplantation genetic diagnosis for infertility or repeated pregnancy loss. INTERVENTION(S): As determined by each evaluated study, the number of biopsied cells and its effect on further development was evaluated by a comparison of models of embryo freezing and partial cell loss. MAIN OUTCOME MEASURE(S): Use of probes, fixation strategy, number of biopsied cells, and error rate determination of different published studies. RESULT(S): Differences in results between studies can be explained by the technology used and are not affected necessarily by differences in design and patient allocation. CONCLUSION(S): Studies that contradict the finding that aneuploidy screening improves implantation and lowers miscarriage rates all have > or =1 of the following aspects in common: (I) an excess of cells having been removed; (II) inadequate choice of probes; and (III) suboptimal fixation technology.