Influence of endometrial thickness on pregnancy rates in modified natural cycle frozen‐thawed embryo transfer

Abstract

Given that endometrial thickness was not found to be predictive of pregnancy after mNC-FET, cancellation based on endometrial thickness alone may not be justified.

Thin Endometrium Is Also Associated With Lower Clinical Pregnancy Rate in Unstimulated Menstrual Cycles: A Study Based on Natural Cycle IVF

“…In all studies published to date, the association of endometrial thickness with pregnancy rate was performed only with high-dose IVF stimulations, cryopreserved embryos (12) or low-dose IUI stimulations. The IVF studies suggested an increase in the pregnancy rate with an endometrium >7 mm (3), whereas the IUI studies failed to demonstrate such a relationship (8).…”

The effect of endometrial thickness on pregnancy outcomes of frozen-thawed embryo transfer cycles which underwent hormone replacement therapy

“…The study of K.E.Liu et al calculated the ORs and their 95% CIs for ongoing pregnancy outcomes with different cut-off values of EMT, and the authors concluded that ongoing pregnancy likelihood was significantly higher in patients with EMT � 9 mm as compared to those who had EMT 3-8 mm [14]. A retrospective study of FET cycles by Tarek El-Toukhy et al compared patients whose endometrial thickness were < 7 mm, 7-8 mm, 9-14 mm and > 14 mm, and found that those with the endometrial thickness of 9-14 mm on the day of progesterone supplementation had higher rates of implantation and pregnancy rates [5]. As with most of the previous studies, in the study of Zhiqin Bu et al, all patients were classified into three groups (Group A, EMT � 8 mm; Group B, EMT 9-13 mm; Group C, EMT � 14 mm) according to the endometrial thickness on the ET day.…”

“…It is noteworthy that this study is the first to report a minimum threshold of endometrial thickness for optimal pregnancy outcomes. Several studies in the past merely reported a relatively broad range of endometrial thicknesses that were considered optimal for pregnancy outcomes while the classification of endometrial thickness in their studies was arbitrary, being mainly based on clinical experience or references [5,9,14], while the range of endometrial thickness in each group was also very large, thus making these studies unlikely of being able to provide good guidance for clinical practice. The result of threshold effect analysis showed that 8.7 mm was the lowest threshold of endometrial thickness for the optimal live birth rate of 50.61%.…”

“…Endometrial thickness (EMT) is the most widely used prognostic indicator for measuring endometrial receptivity. Although observations suggest that the association between EMT and IVF outcomes is still contradictory and inconsistent [4,5], there is a general consensus that thin endometrium is associated with low pregnancy rate. Furthermore, several studies have shown that there is a correlation between EMT and clinical pregnancy outcome after conducting FET [6,7].…”

Endometrial thickness in modified natural‐cycle frozen‐thawed embryo transfer cycles: Should we ignore the red traffic lights?

“…Sir, Groenewoud et al recently concluded that endometrial thickness does not predict fertility success in modified natural-cycle frozenthawed embryo transfer (mNC-FET) cycles. 1 They suggest that embryo transfer can be planned regardless of endometrial thickness.…”