2012년 유럽불임학회 (ESHRE) P-200 The pregnancy potential of the late cleaved- embryos on day 3 is similar to 8-cell embryos on day 3 in FETs. (3일째 동결란 이식하는 경우 늦게 분열하는 수정란과 8세포의 수정란 사이에 임신능력의 차이는 유사하다.)

J.H. Lee1, K.H. Lee2, I.H. Park1, H.G. Sun1, S.G. Kim1, Y.Y. Kim1, E.M. Choi1.
1Mamapapa&baby Obstetrics Gynecology Clinic, Infertility Lab., Ulsan city, Korea South.

INTRODUCTION

Pregnancy rate was reportedly higher with the transfer of embryos that are more developmentally advanced on day 3, and higher for transfer of 8-cell embryos compared with late cleaved-embryos. However, these studies, because they are based on fresh embryo transfers, are unable to distinguish between the effects of embryo quality and endometrial receptivity. The objective of this study is to evaluate the relationship between pregnancy potential of the late cleaved-embryos in frozen thawed embryo transfers (FETs), independent of endometrial receptivity.

MATERIALS AND METHODS

We analyzed 296 cycles from patients underwent FETs from November 2009 to November 2011. Cryopreserved embryos were transferred to patients either in natural cycle or in a hormonally manipulated artificial cycle following preparation of the endometrium with estradiol and progesterone. Embryos were frozen on day 3 using a vitrification protocol. Frozen embryos developed to 8 cell were thawed on the day of transfer (group A, n=194). Late cleaved embryos were thawed on day 2 (group B, n=102) and cleaved to 8-cell were selected for transfer. And FETs were performed by same physician on day 3. We compared survival rates, fully intact rates, and pregnancy rates.

RESULTS

There were no differences between both groups in patient age (35±4.4 in group A vs. 34±3.9 in group B), endometrial thickness (9.2±1.9 vs. 9.5±2.0), fully intact rates (69.2% vs. 66.9%), and survival rates (83.6% vs. 81.3%). And there was difference in the mean number of blastomeres per frozen embryo between groups (7.4±1.5 vs. 5.4±1.2). But after thawing mean number of blastomeres per embryo transferred did not differ between groups (7.8±1.4 vs. 7.5±1.6). Also the two groups did not differ as to pregnancy rates (41.8% vs. 39.2%).

CONCLUSION

In generally, the late cleaved-embryos have low pregnancy potential in fresh embryo transfer cycles. But in FETs pregnancy rate of the late cleaved- embryos on day 3 is similar to that of 8-cell embryos on day 3. Low implantation potential of the late cleaved-embryos can be overcome by thawing 1 day before ET, in FETs. Therefore the late cleaved-embryo cryopreservation may be an effective alternative to fresh embryo transfer.