Recently, advances in human IVF-embryo transfer (ET) have been reported using sequential media and blastocyst stage ET. In our previous report, using a prospective, randomized study, no advantage was found using the blastocyst stage ET compared with day 3 ET. This study was performed in order to evaluate implantation and pregnancy rates of hatching blastocyst stage ET compared with conventional day 3 ET.METHODS AND RESULTS
A total of 480 patient cycles were evaluated using a prospective, randomized study. The pregnancy rate and implantation rate were compared between the day 3 ET (n=240) and hatching blastocyst stage ET (Hat ET; n=240). The Hat ET group had a pregnancy rate of 29.3% (55 out of 188) and an implantation rate of 21.4% (67 out of 313). The day 3 ET group had a pregnancy rate of 29.2% (70 out of 240) and an implantation rate of 19.1% (93 out of 488). In the Hat ET group, the pregnancy rate, implantation rate and ongoing pregnancy rate of day 5 ET and day 6 ET were all higher than the respective rates in the day 7–9 ET group.CONCLUSION
We found that the pregnancy rate and implantation rate of ET with hatching stage blastocysts had no advantage compared with the conventional day 3 ET.