What is the Optimal Timing of Embryo Transfer When there are only up to Two Embryos at Cleavage Stage?

Introduction: Not only has there been a debate whether embryo transfer should be performed at the cleavage stage or at the blastocyst stage but there is also uncertainty regarding when to transfer if there are only one or two embryos at the cleavage stage.

Aim: 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 at the cleavage stage on day 3.

Material and methods: A retrospective cohort study. 527 patients were included in the study. Between January 2012 and October 2017, 100 patients with one or two cleavage stage embryos had their embryos transferred on day 3 and 427 patients had their embryos cultured to day 5 for transfer.

Results: The average number of oocytes (5.9 vs 6.5, p=NS), mature oocytes (4.0 vs 4.6, p=NS) and number of cleavage stage embryos on day 3 was similar in the two groups (1.3 vs. 1.5, p=NS). The clinical pregnancy rate per retrieval (22% vs. 25%, p=NS) and the ongoing pregnancy rate per retrieval (20% vs. 20.5%, p=NS) were comparable between the two groups. Fifty-seven (13.2%) of the patients had cleavage embryo arrest and didn’t have any embryo to transfer on day 5.

Conclusions: The cumulative pregnancy rate is the same for patients with 1-2 cleavage stage embryos regardless of whether the embryo is transferred on day 3 or day 5.