Endometrial thickness and growth during ovarian stimulation: a possible predictor of implantation in in vitro fertilization.

The present study was undertaken to evaluate endometrial thickness and the amount of endometrial growth (delta) in patients who conceived during in vitro fertilization (IVF) (n = 36) compared with matched women who did not conceive (n = 72). Estradiol (E2) and endometrial thickness were measured daily from cycle day 10 to the day after human chorionic gonadotropin (hCG). Mean endometrial thickness and E2 levels on cycle day 10 did not differ. On the day before ovum retrieval, significantly thicker endometrium was observed in the pregnant than in the nonpregnant women (8.6 +/- 0.3 [SEM] and 7.1 +/- 0.3 mm, respectively; P less than 0.0005), whereas the mean E2 levels did not differ. The delta endometrial growth was greater in the women who conceived than in the nonpregnant group (4.3 +/- 0.2 and 2.5 +/- 0.2 mm, respectively; P less than 0.0005). The fertilization rate and serum E2 levels did not correlate with endometrial thickness nor with delta endometrial growth. Our data suggest that the amount of endometrial growth during ovarian hyperstimulation and the endometrial thickness on the day before oocyte retrieval deserve further study as possible predictive parameters for implantation.