RESUMEN
In 53 patients of an in vitro fertilization (IVF) program with unsuccessful fertilization of oocytes, an endometrial biopsy was carried out on the day of the intended embryo transfer. The results were compared with the thickness (assessed on the very same day by means of ultrasonography) and the echo pattern of the endometrium, which was classified into four grades (A to D). We found grade A in 16 cases (30%), grade B in 22 cases (41.5%) and grade C in 15 cases (28.5%); no endometrium was assessed as grade D. The distribution of histologic findings was not significantly skewed within the respective grading categories (only 37.5% of grade A endometria, 63.5% of grade B endometria and 66.5% of grade C endometria were in phase with the menses). The in-phase and out-of-phase endometria did not display significant differences in endometrial thickness (8.8 +/- 0.29 mm vs. 9.13 +/- 0.4mm). Neither the sonographically measured endometrial thickness nor the echo pattern correlated with the histologic findings, suggesting that ultrasonography is inadequate for drawing reliable conclusions about endometrial receptivity in an IVF program.