Relationship between endometrial thickness and embryo implantation, based on 1,294 cycles of in vitro fertilization with transfer of two blastocyst-stage embryos

Abstract

Objective: To evaluate the relationship between endometrial thickness and clinical outcome of IVF and ET.

Design: Retrospective study.

Setting: Private assisted reproductive technology center.

Patients: One thousand two hundred and ninety-four infertility patients.

Interventions: IVF and fresh autologous ET of two blastocyst-stage embryos, including at least one good-quality blastocyst.

Main outcome measures: Clinical pregnancy rate (PR) and spontaneous abortion rate.

Results: Endometrial thickness was greater in cycles resulting in pregnancy than in cycles not resulting in pregnancy (11.9 vs. 11.3 mm, respectively). Clinical pregnancy rates increased gradually from 53% among patients with a lining of <9 mm, to 77% among patients with a lining of > or =16 mm. Multiple logistic regression analysis indicated significant effects of age, embryo quality, and endometrial thickness on both clinical pregnancy rates and live-birth or ongoing pregnancy rates. There was also a marginally significant trend toward decreasing rates of spontaneous pregnancy loss with increasing endometrial thickness.

Conclusions: Clinical pregnancy and live-birth or ongoing pregnancy rates increase significantly with increasing endometrial thickness, independent of the effects of patient age and embryo quality.