Early blastulation (EB) of day 4 embryo is predictive of outcomes in single embryo transfer (SET) cycles

The aim of this study was to assess whether the early blastulation (EB) of day 4 embryo is a useful predictor for outcomes in fresh elective single embryo transfer (eSET) cycles.

We retrospectively enrolled patients undergoing fresh SET cycles in our hospital from April 2014 to September 2016 and met with the following criteria: 1) age <38 years, 2) first IVF/ICSI cycle, 3) at least two blastocysts with morphological grading better than or equal to 4BB.

A total of 81 patients were included. Of whom, 55 patients (68%) had undergone eSET with embryos that had early blastulation on day 4 while the other 26 patients had had no EB. Early blastulation has shown a higher rate of good blastocyst (84.3% vs. 60.5%, p < 0.0001). The clinical pregnancy rate of EB group was significantly higher than that of non-EB group (56.4% vs. 27.0%, p = 0.013). There is also a tendency in EB group to have a lower abortion rate (3.23% vs. 28.6%, p = 0.081).

EB on day 4 is a useful predictor of the quality of the following embryos (i.e. day 5 embryo). It is a simple tool in selecting the best embryo to get a higher pregnancy rate in fresh eSET cycles.

This study was supplementally registered by the MacKay Memorial Hospital Institutional Review Board on April 18, 2017 (registration No. 17MMHIS039e).