The deferred embryo transfer strategy improves cumulative pregnancy rates in endometriosis-related infertility: A retrospective matched cohort study

Background Controlled ovarian stimulation in assisted reproduction technology (ART) may alters endometrial receptivity by an advancement of endometrial development. Recently, technical improvements in vitrification make deferred frozen-thawed embryo transfer (Def-ET) a feasible alternative to fresh embryo transfer (ET). In endometriosis-related infertility the eutopic endometrium is abnormal and its functional alterations are seen as likely to alter the quality of endometrial receptivity. One question in the endometriosis ART-management is to know whether Def-ET could restore optimal receptivity in endometriosis-affected women leading to increase in pregnancy rates. Objective To compare cumulative ART-outcomes between fresh versus Def-ET in endometriosis-infertile women. Materials and methods This matched cohort study compared def-ET strategy to fresh ET strategy between 01/10/2012 and 31/12/2014. One hundred and thirty-five endometriosis-affected women with a scheduled def-ET cycle and 424 endometriosis-affected women with a scheduled fresh ET cycle were eligible for matching. Matching criteria were: age, number of prior ART cycles, and endometriosis phenotype. Statistical analyses were conducted using univariable and multivariable logistic regression models. Results 135 in the fresh ET group and 135 in the def-ET group were included in the analysis. The cumulative clinical pregnancy rate was significantly increased in the def-ET group compared to the fresh ET group [58 (43%) vs. 40 (29.6%), p = 0.047]. The cumulative ongoing pregnancy rate was 34.8% (n = 47) and 17.8% (n = 24) respectively in the Def-ET and the fresh-ET groups (p = 0.005). After multivariable conditional logistic regression analysis, Def-ET was associated with a significant increase in the cumulative ongoing pregnancy rate as compared to fresh ET (OR = 1.76, CI95% 1.06-2.92, p = 0.028). Conclusion Def-ET in endometriosis-affected women was associated with significantly higher cumulative ongoing pregnancy rates. Our preliminary results suggest that Def-ET for endometriosis-affected women is an attractive option that could increase their ART success rates. Future studies, with a randomized design, should be conducted to further confirm those results.