Can Fresh Embryo Transfers be Replaced by Cryopreserved-Thawed Embryo Transfers in Assisted Reproductive Cycles? A Randomized Controlled Trial

Aflatoonian A *, Oskouian H , Ahmadi S ,


Objective: 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 frozen-thawed embryo transfer (FET) cycles than fresh embryo transfer (ET) cycles. The objective of this study was to compare ongoing pregnancy rate between fresh ET and FET cycles in ART. 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 < 0.05]. Implantation clinical pregnancy and multiple pregnancy rates were also higher in FET group. Conclusion: FETs can be performed instead of fresh ETs to improve the outcome of ART cycles in highly selected patients.