The factors affecting the outcome of frozen–thawed embryo transfer cycle

OBJECTIVE: To determine the impact of the clinical and embryological factors on the pregnancy outcome of frozen-thawed embryo transfer. MATERIALS AND METHODS: The data of 247 frozen-thawed embryo transfer cycles were assessed at Royan Institute from March 2006 to March 2008. Appropriate statistical analysis was performed using Student t test and Chi-square or Fisher exact test. Forward logistic regression was done to predict the individual impact of factors on the success of frozen embryo transfer. RESULTS: According to our results, 1,523 frozen embryos were thawed with a survival rate of 79.8%. The overall chemical and clinical pregnancy rates per embryo transfer cycle were 28.1% and 26.3%, respectively. A total of 71 gestational sacs were implanted (7.9%). The pregnancy outcome was higher in women who were stimulated with the gonadotrophin releasing hormone agonist long protocol, treated by a combination of follicle stimulating hormone and luteinizing hormone, who had endometrial thickness greater than or equal to 8mm on the embryo transfer day, and who had positive fresh-cycle pregnancy test. CONCLUSION: Protocol type, gonadotrophin preparations, fresh-cycle outcome, endometrial thickness and the numbers of obtained oocytes, embryos, and high-quality thawed embryos transferred are the factors affecting pregnancy outcome of frozen-thawed embryo transfer.