The endometrium in assisted reproductive technology: How thin is thin?

Area of Science:

• Reproductive Endocrinology
• Assisted Reproductive Technology

Background:

• A thin endometrium (<6 mm) occurs in 2.4% of assisted reproductive technology (ART) cycles.
• It is associated with significantly lower implantation and pregnancy rates.
• The etiology of a thin endometrium impacts endometrial receptivity (ER).

Purpose of the Study:

• To review the implications of a thin endometrium in ART.
• To explore the role of hormone replacement therapy (HRT) in frozen embryo transfer (FET) cycles.
• To discuss the utility of endometrial receptivity testing for thin endometria.

Main Methods:

• Literature review of studies on thin endometrium in ART.
• Analysis of pregnancy and implantation rates based on endometrial thickness.
• Evaluation of treatment strategies and diagnostic tests for ER.

Main Results:

• Endometrial thickness <6 mm shows a trend toward lower pregnancy probability.
• HRT-FET cycles demonstrate improved ER and potentially better outcomes.
• No validated treatments currently exist to enhance endometrial growth.

Conclusions:

• A thin endometrium is a significant concern in ART, impacting success rates.
• HRT-FET cycles may offer improved outcomes by enhancing ER.
• Endometrial receptivity array testing can provide reassurance for patients with thin endometria before FET.