Follicular phase length has no influence on frozen-thawed embryo transfers in natural cycles

Ying Ying,Fuman Qiu,Haiying Liu,Sichen Li,Jianqiao Liu,Qing Huang

doi:10.1186/s13048-020-00690-z

Abstract

BackgroundWhether menstrual variability in women with regular and ovulatory cycle could affect embryo implantation remains controversial, with conflicting evidences presented in the literature. Thus, in this study, we evaluated the impact of prolonged follicular phase length (FPL) on the clinical pregnancy rate (CPR) after frozen–thawed embryo transfer (FET) in true natural cycles (NC).MethodsThis retrospective cohort study utilized data from a large university-affiliated reproductive medicine center. Women undergoing true NC-FET were grouped as per their FPL type: Prolonged FPL (n = 127) and Normal FPL (n = 737). The primary study outcome was CPR in these 2 groups.ResultsThe FPL in the current cycle was significantly longer in the Prolonged FPL group (23.0 ± 2.4) than in the Normal FPL group (16.0 ± 2.2; p < 0.001). The crude CPR was significantly higher in the Prolonged FPL group (61.4%) than in the Normal FPL group (51.7%; p = 0.043). After adjusting for the results of potential confounders including the age, BMI, percent of optimal embryos transferred, and endometrial thickness, the difference in the CRP between the 2 groups disappeared (OR 1.28, 95% CI: 0.86–1.91, p = 0.232). No statistically significant difference was noted in the rates of implantation and miscarriage.ConclusionsThe current FET should not be cancelled if the ovulation time exceeds the predicted period based on the length of the previous menstrual cycle in the light of no negative effect on the pregnancy outcome.

Highlights

Whether menstrual variability in women with regular and ovulatory cycle could affect embryo implantation remains controversial, with conflicting evidences presented in the literature
864 cycles of true natural cycles (NC)-frozen– thawed embryo transfer (FET) were included in the present analysis, which were divided into 2 groups depending on the ovulation day of present menstrual cycle for FET (Fig. 1)
Patients in the Prolonged follicular phase length (FPL) group showed a higher percent of optimal embryos transferred at the cleavage-stage (65.8% vs 53.1%, p = 0.044) and significantly thicker endometrial thickness (8.64 ± 1.34 vs 8.32 ± 1.37, p = 0.004) when compared with those in the Normal FPL group

Summary

Introduction

Whether menstrual variability in women with regular and ovulatory cycle could affect embryo implantation remains controversial, with conflicting evidences presented in the literature. In this study, we evaluated the impact of prolonged follicular phase length (FPL) on the clinical pregnancy rate (CPR) after frozen– thawed embryo transfer (FET) in true natural cycles (NC). The optimal timing for NC-FET should be considered carefully with due consideration to the luteinizing hormone (LH) surge by serum monitoring in combination with a decrease in the serum estradiol level and an increase in the serum progesterone. An intensive monitoring of spontaneous ovulation is essential for timely determination of NC-FET. Delay in the ovulation of a considerable number of patients with regular menstrual cycle was detected, which raises the question of whether the prolonged follicular phase had a detrimental effect on the endometrial receptivity, which in turn led to implantation failure in ovulation-delayed patients

Methods

Results

Discussion

Conclusion