What is the optimal timing of embryo transfer when there are only one or two embryos at cleavage stage?

Today, most IVF programs have moved to blastocyst transfer but there is still uncertainty regarding when to transfer if there are only one or two embryos at the cleavage stage. The aim of this study was to compare the pregnancy rate of day 3 transfers vs. blastocyst stage transfers in patients who had only one or two embryos on day 3. We conducted a retrospective study of 102 patients with one or two cleavage stage embryos that had their embryos transferred on day 3 and 429 patients had their embryos cultured to day 5 for transfer. The number of mature oocytes (4.0 vs 4.6