Predicting factors for endometrial thickness during treatment with assisted reproductive technology

To discover the factors contributing to endometrial thickness, and to assess the impact of endometrial thickness on pregnancy rates (PRs) according to these factors.

Retrospective study.

In vitro fertilization unit in a university hospital.

All women with primary infertility and no previous pregnancies who underwent IVF treatment at the Chaim Sheba Medical Center, Tel Hashomer, Israel, between August 9, 2001-December 31, 2004.

Measurement of endometrial thickness by the use of transvaginal ultrasound probe on the day that hCG was administered during an IVF cycle.

Factors influencing endometrial thickness and the relationship between endometrial thickness and PRs.

The mean endometrial thickness decreased as a function of the patient's age. The thickest endometrium was found in patients <25 years of age (11.9 +/- 2.5 mm), and the thinnest endometrium was found in patients >40 years of age (9.6 +/- 2.3 mm). Other factors, such as E(2) levels, etiology of infertility, induction of ovulation protocol, and type of gonadotropin used, were also found to contribute to endometrial thickness.

Our data support the case for an "aging" of the endometrium. The chances of achieving a thick endometrium for patients >40 years of age are lower than for younger patients. Furthermore, a thicker endometrium is correlated with a higher PR only for patients >35 years of age.