Preparation of endometrium for frozen embryo replacement cycles: a systematic review and meta-analysis

Abstract

Purpose The purpose of this study was to evaluate the best protocol to prepare endometrium for frozen embryo replacement (FER) cycles. Methods This study is a systematic review and meta-analysis. Following PubMed and OvidSP search, a total of 1166 studies published after 1990 were identified following removal of duplicates. Following exclusion of studies not matching our inclusion criteria, a total of 33 studies were analyzed. Primary outcome measure was live birth. The following protocols, including true natural cycle (tNC), modified natural cycle (mNC), artificial cycle (AC) with or without suppression, and mild ovarian stimulation (OS) with gonadotropin (Gn) or aromatase inhibitor (AI), were compared. Results No statistically significant difference for both clinical pregnancy and live birth was noted between tNC and mNC groups. When tNC and AC without suppression groups are compared, there was a statistically significant difference in clinical pregnancy rate in favor of tNC, whereas it failed to reach statistical significance for live birth. When tNC and AC with suppression groups are compared, there was a statistically significant difference in live birth rate favoring the latter. Similar pregnancy outcome was noted among mNC versus AC with or without suppression groups. Similarly, no difference in clinical pregnancy and live birth was noted when ACs with or without suppression groups are compared. Conclusions There is no consistent superiority of any endometrial preparation for FER. However, mNC has several advantages (being patient-friendly; yielding at least equivalent or better pregnancy rates when compared with tNC and AC with or without suppression; may not require LPS). Mild OS with Gn or AI may be promising.

Can letrozole plus HMG protocol improve pregnancy outcomes in frozen-thawed embryo transfer? An RCT

“…In another study in 2016, modified natural withthe artificial cycle for cryo-thawed embryo transferwere compared and it was observed observed that there is no significant differences in live birth rate (11.5% vs. 8.8%) and clinical pregnancy rate (19% vs. 16.0%) between two groups of modified NC-FET and AC-FET(12). A recent meta-analysis by Yarali et al shows that at the moment there is not sufficient evidence to support the use of any protocols (13). …”

“…In AC-FET the endometrium is prepared by estradiol and progesterone hormones with or without GnRH-agonist. There are different studies for comparison of these protocols (10-13). …”

Endogenous progesterone levels could predict reproductive outcome in frozen embryo replacement cycles supplemented with synthetic progestogens: A retrospective cohort study

“…So far, according to numerous reviews, no endometrial preparation regime (natural or supplemented cycle) or a combination of specific drugs has proved itself superior compared to other alternative FER protocols . In our study, we have used dydrogesterone which is an orally administered synthetic progestogen that has been successfully used for luteal‐phase support in stimulated IVF cycles for many decades .…”

“…Parallel to these developments, endometrial preparation protocols have evolved little since their first description. To date, according to several systematic reviews, no endometrial preparation regime or a combination of specific drugs has proved itself superior compared to any other protocol . Supplemented estrogen/progesterone‐based protocols are convenient because they require minimal monitoring and could be easily scheduled.…”

The role of frozen–thawed embryo replacement cycles in assisted conception

“…The limited available evidence shows equivalent pregnancy rates between gonadotrophin FER and both medicated and natural cycle FER. [84][85][86] However, gonadotrophin protocols are complicated, involve intensive monitoring and carry a risk of OHSS. Consequently, the use of gonadotrophin for FER is uncommon.…”