Endometrial Thickness and Reproductive Outcomes

Predictive Value of Endometrial Thickness

A meta‑analysis of 1,525 patients undergoing intra‑uterine insemination found no statistically significant association between endometrial thickness and clinical pregnancy rates, indicating that thickness alone does not predict success. Evidence level: meta‑analysis (moderate‑to‑high quality) 1, 2.
Overall, the literature rates endometrial thickness as a poor prognostic marker for fertility treatment outcomes, with the supporting evidence judged to be of low to moderate quality. Evidence level: low‑to‑moderate quality 1, 2.

Comparative data show that clomifene citrate is associated with a significantly thinner endometrium compared with gonadotropin‑based stimulation protocols in assisted reproduction cycles. Evidence level: observational studies (moderate quality) 1, 2.

Multiple studies report that body mass index (BMI) does not have a meaningful effect on endometrial thickness in the majority of examined populations. Evidence level: cohort studies (moderate quality) 3, 4.

Proceed with single‑embryo transfer when the endometrial thickness is ≥ 6 mm; pregnancies have been documented even with thinner linings, and the decision to transfer should not be based solely on endometrial measurements. (Evidence not graded; recommendation derived from systematic review) 5

The European Society of Human Reproduction and Embryology (ESHRE) issues a strong recommendation that endometrial characteristics must not dictate whether an embryo transfer is performed in either fresh or frozen cycles. (Strong recommendation) 5

ESHRE strongly advises against increasing the number of embryos transferred because of thin endometrium; doing so raises the risk of multiple pregnancy approximately 30‑fold without improving live‑birth outcomes. (Strong recommendation) 5