P-492 The relationship between dominant follicle development and clinical outcomes of hormone replacement therapy-frozen embryo transfer: a retrospective clinical study
Authors: Xing J , Huang C 
Published: June 2023

Study question

Dose the dominant follicle development occurred in the hormone replacement therapy-frozen embryo transfer cycles affect the clinical pregnancy outcomes?

Summary answer

The development of dominant follicles in HRT-FET cycles does not affect the clinical pregnancy rate, early miscarriage rate and live birth rate.

What is known already

The hormone replacement therapy is one of the most commonly used endometrial preparation protocols for frozen embryo transfer due to the convenience of administration and stability of pregnancy outcomes. Howere, here are 4-10% cycles accompanied by the development of dominant follicles.In order to avoid uncontrollable follicular development in HRT cycles, clinicians tried to increase the dosage of exogenous oestrogen or take oestrogen in advance, which still could not totally inhibit follicular growth. In addition, gonadotropin releasing hormone agonist is also used. However, excessive GnRHa use will increase the treatment cost and prolong the treatment time.

Study design, size, duration

This is a noninterventional, retrospective, observational, single-centre cohort study. From 2012 to 2019, 13251 cycles were included in this study.

Participants/materials, setting, methods

This study involved 13251 HRT-FET cycles. In 13107 cycles , there was no dominant follicle development in HRT cycles, while in 144 cycles, there was dominant follicle development. We used a multivariable logistic regression model and adopted propensity-score matching, in order to study the impact of dominant follicle development on the clinical pregnancy outcomes of HRT-FET cycles, and aim to clarify the appropriate criteria for canceling HRT-FET cycles with dominant follicle development.

Main results and the role of chance

Considering the differences in the number of cycles and baseline characteristics between the two groups, we adopted propensity-score matching to identify the cycle cohort with similar baseline characteristics. After propensity-score matching, the baseline characteristics of patients in the two groups were similar. There was no difference in the number of transferred embryos and the proportion of transferred blastocysts between the two groups. There was no significant difference in clinical pregnancy rate, early miscarriage rate and live birth rate between the two groups. In addition, univariate analysis was also used to identify confounding factors that may affect clinical pregnancy outcomes). The baseline factors (female age, male age, AFC, baseline FSH level, infertility duration, number of previous embryo transfer cycles) and treatment factors (endometrium thickness, number of transferred embryos and type of transferred embryos) were selected as the adjustment variables of multivariate regression analysis. There was no significant correlation between dominant follicular development in HRT-FET cycles and clinical pregnancy rate (adjusted OR = 1.162, 95% CI: 0.737-1.832, P = 0.52).

Limitations, reasons for caution

The main limitation of this study is the retrospective design. In addition, there is a significant difference between two groups. In a real life setting, these results are cautiously applicable.Further prospective investigations are needed to elucidate the impact of dominant follicle development on clinical outcomes.

Wider implications of the findings

Our retrospective study suggests that the development of dominant follicles in HRT-FET cycles does not affect the clinical pregnancy rate, early miscarriage rate and live birth rate. Therefore, it is not necessary to cancel the FET cycle immediately when the dominant follicle development is monitored in the HRT-FET cycle.

Trial registration number

not applicable