Impact of cleavage-stage embryo biopsy in view of PGD on human blastocyst implantation: a prospective cohort of single embryo transfers.

BACKGROUND Human embryo biopsy is performed for preimplantation genetic diagnosis (PGD). The impact of 1- or 2-cell removal at cleavage-stage on future embryo development and implantation capacity is highly debated. METHODS In order to explore this issue further, a cohort of Day 5 single embryo transfers was analysed prospectively for embryological and clinical outcome. All transferred embryos resulted from 8-cell embryos on Day 3, from which subsequently either one cell (group I, n = 182) or two cells (group II, n = 259) were removed, or on which no invasion by means of embryo biopsy was performed (group III, control group, n = 702). RESULTS Blastocyst formation was significantly better in group III compared with group II, and similar to group I. Group I and group II did not differ in Day 3 nor in Day 5 embryo development. The overall live birth rate was significantly higher in group I (37.4%, CI 29.0-47.4%) than in group II (22.4%, CI 17.0-28.9%), and comparable to the reference ICSI population (35.0%, CI 30.8-39.7%). CONCLUSIONS The clinical outcome of 1-cell biopsy was significantly better than that of 2-cell biopsy, even when adjusted for availability of genetically transferable embryos.