The Analysis of Factors Affecting the Success Rate of Frozen Thawed Embryos in IVF / ICSI Cycles

Purpose: the aim of this study is to analyze the factors contributing to the success of frozen- thawed embryo transfer (ET). Material and method: This retrospective, case-control study was carried out on 700 infertile couples treated with IVF and ICSI and had embryo freezing in Isfahan Fertility and Infertility Center, Iran, from the beginning of July 2000 to the end of June 2003. Results: factors affecting the success rate of frozen- thawed ET are: the number of 7-8 cell embryos with survival rate > 75%, the ratio of frozen-thawed embryos with survival rate > 75% to the total number of frozen-thawed embryos, the number of frozen embryos, mean percentage viability ,cleavage stage of fresh embryos, and mean viability percentage of frozen- thawed embryos. Significantly correlated factors with the number of frozen-thawed 7-8 cells embryos with survival rate > 75% are the number of type A fresh 7- 8 cell embryos, fresh embryo survival rate and cellular staging, the number of embryos on the third day following insemination, fresh embryo survival coefficient, the number of retrieved oocytes, and maternal age (with a negative correlation). Discussion: increasing the viability percentage and number of cryopreserved embryos increases the success of frozen-thawed ET. Among all, the number of 7-8 cell embryos with survival rate > 75% are the most influential ones. Also, improving the before freezing such as the number of retrieved oocytes and the number and quality of embryos improves the viability percentage and number of frozen- thawed embryos.