Freeze all policy: fresh versus elective frozen-thawed embryo transfer

Abstract

Controlled ovarian stimulation (COS) may adversely affect endometrial receptivity during in vitro fertilization (IVF) cycles. It has been suggested that supraphysiologic hormonal levels during COS, mainly progesterone elevation (PE) on the day of human chorionic gonadotropin administration, are associated with a decreased probability of pregnancy in fresh cycles; in these cases, the patient may benefit from frozen-thawed embryo transfer (FET). The main objective of this study was to compare IVF outcomes between fresh embryo transfer and elective FET (freeze all policy), considering that fresh embryo transfers were performed only in cases without progesterone elevation. Prospective observational cohort study. The study was conducted between January 2012 and December 2013. Accepting an alpha risk of 0.05 and a beta risk of 0.2 in a two-sided test, at least 229 subjects in each group were necessary to recognize a relative risk ≥1.3 as statistically significant. A total of 625 patients submitted to COS with gonadotropin-releasing hormone (GnRH) antagonist protocol and day3 embryo transfer were included. In the fresh group (n=372), embryo transfers were performed only if progesterone levels were ≤1.5 ng/mL on the trigger day. The freeze-all group (n=253) comprised patients that had all embryos cryopreserved in the fresh cycle and had the first embryo transfer after endometrial priming and embryo thawing. Data were described as the mean ± standard deviation or percentages. The statistical analysis was performed using Student’s t test, the chi-square test, and linear regression models. A p value of <0.05 was considered statistically significant. The main outcome measure was ongoing pregnancy rate. IVF outcomes in fresh and freeze-all groups are expressed in the table below.Tabled 1Fresh group (n=372)Freeze all group (n=253)RR (95% CI)p valueAge, years ±SD35.48±5.1234.79±4.040.064nET±SD2.26±0.782.09±0.580.001IR, %20.126.41.30 (1.07-1.59)0.008CPR, n (%)142 (38.1)117 (46.2)1.21 (1.01-1.46)0.042OPR, n (%)122 (32.8)103 (40.7)1.24 (1.01-1.53)0.041CPR: clinical pregnancy rate; IR: implantation rate; nET: number of embryos transferred; OPR: ongoing pregnancy rate Open table in a new tab CPR: clinical pregnancy rate; IR: implantation rate; nET: number of embryos transferred; OPR: ongoing pregnancy rate IVF outcomes were significantly greater in the freeze-all group compared to the fresh group. These results suggest that even in a selected group of patients for fresh embryo transfer (progesterone levels ≤1.5 ng/mL), endometrial receptivity may be impaired by the COS, and outcomes may be improved by performing the freeze all policy.