Clinical outcome of day 2 versus day 5 transfer in cycles with one or two developed embryos

Objective: To determine whether extended culture of embryos to blastocysts has any benefit in cycles with only one or two created embryos. Design: Retrospective analysis of cycles comparing outcomes of day 2 and day 5 transfers. Our day 2 group was from the year 1999 and our day 5 croup, from the year 2000. Setting: Assisted reproductive technology program of a teaching hospital. Patient(s): All patients, irrespective of age, who had developed one or two embryos. Intervention(s): Stimulated IVF, intracytoplasmic sperm injection, or testicular sperm extraction and intracytoplasmic sperm injection cycles with 2-day culture in universal IVF medium (n = 133) or 5-day culture in BlastAssist media (MediCult, Jyllinge, Denmark; n = 132). Main Outcome Measure(s): Pregnancy, implantation, and take-home baby rates. Result(s): In the groups of 2-day and 5-day culture, embryo transfer was performed in 98% and in 57% of cycles, respectively. However, the total implantation rate per created embryo (18% vs. 18%), the pregnancy rate per cycle (23% vs. 21%), and the take-home baby rate (69.4% vs. 71.4%) did not differ between the day 2 and day 5 groups. Conclusion(s): Extended culture of embryos does not improve or decrease their capacity for implantation but only allows for better selection and is therefore not necessary in cycles with fewer than three embryos. (Fertil Stefil((R)) 2002;77:529-36. (C) 2002 by American Society for Reproductive Medicine).