Improved clinical outcomes for in vitro fertilization with delay of embryo transfer from 48 to 72 hours after oocyte retrieval: use of glucose- and phosphate-free media.

OBJECTIVE: To evaluate clinical outcomes of day 2 versus day 3 ET using a culture media with no glucose or phosphate. DESIGN: Retrospective clinical study. SETTING: Hospital-based fertility clinic. PATIENT(S): One hundred seventy-six IVF-ET patients undergoing controlled ovarian supraovulation. INTERVENTION(S): IVF and delaying the ET by 1 day. MAIN OUTCOME MEASURE(S): Number of blastomeres per embryo, implantation and pregnancy rates. RESULT(S): Delaying the ET from day 2 to day 3 after oocyte retrieval significantly increased implantation rates (13% versus 24%) and ongoing/delivered pregnancy rates per retrieval (26% versus 44%). Day 3 embryos with > or = 8 blastomeres resulted in a significantly higher pregnancy rate (53%) than day 3 embryos with < 8 cells (23%) and day 2 embryos with > or = 4 cells (31%) or < 4 cells (11%). CONCLUSION(S): Day 3 ET was associated with a significant increase in implantation and pregnancy rates. Delaying the ET until day 3 may permit the selection of more viable embryos than on day 2. The absence of glucose and phosphate from the culture media is compatible with good IVF outcomes.