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

Abstract

Background: Whether 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 frozenthawed embryo transfer (FET) in true natural cycles (NC). Methods: This 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. Results: The 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. Conclusions: The 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.

Follicular phase length is not related to live birth outcome in women with unexplained infertility undergoing ovarian stimulation with intrauterine insemination cycles in a multicenter trial

“…Our results are consistent with recent studies that evaluated the association of FPL and pregnancy outcome in the context of treatment with assisted reproductive technology ( 18 , 19 ) and natural cycle frozen-thawed embryo transfer ( 11 , 20 ). All of these studies report no association between FPL and pregnancy outcomes.…”

“…There is no consensus in the current literature as to a specific cut-off to define short FPL. Consistent with prior studies of natural and stimulated cycles ( 11 , 12 , 13 , 14 , 15 ), this study revealed variation in length of the follicular phase ranging from 7 to 24 days. Recently published studies examined cycle phase lengths in women using mobile phone applications that track the menstrual cycle ( 12 , 14 , 15 , 16 , 17 ).…”