I-29: Can Fresh Embryo Transfers Be Replacedby Cryopreserved-Thawed Embryo Transfers inAssisted Reproductive Cycles? A RandomizedControlled Trial

Background: Controlled ovarian stimulation (COS) has been shown to advance endometrial maturation and affect adversely implantation in assisted reproduction technology (ART) cycles. It has been reported that there is a better embryo-endometrium synchrony in frozenthawed embryo transfer (FET) cycles than fresh embryo transfer (ET) cycles. The Background of this study was to compare ongoing pregnancy rate between fresh ET and FET cycles in ART. According to recent published prospective study from Belgium and our research, the pregnancy outcome after frozen embryo transfer is comparable or even better than pregnancy outcome after fresh embryo transfer. Some studies showed that Vitrification may increase the embryo survival rate and the chance of pregnancy rate. Materials and Methods: In a prospective, controlled study, the patients who were classified as high responders, were randomized to either fresh ET or FET. The embryos in FET group were cryopreserved with vitrification by Cryotop method. Randomization was done on the day of ET according to a computer-generated random numbers. Ongoing pregnancy rate was the primary outcome measure.Results: A total of 374 patients were included, 187 of which were randomized to FET and 187 to fresh ET. There were 39% (n= 73) ongoing pregnancy in FET group compared with 27.8% (n= 52) in fresh ET group [odds ratio (OR) = 1.66; 95% confidence interval (CI) = 1.07-2.56; p