Objective: To compare the changes of sonographic features of endometrium throughout natural and artifi cial cycles in which oral estrogen-progesterone substitution were used in the same group of patients and discuss their clinical signifi cance. Design: A prospective study. Setting: Dept. of Obstetrics and Gynaecology, University Hospital, Olomouc. Methods: In 24 women with regular menstrual cycle ovulation was detected (LH, sonography) and the following sonographic features: endometrial thickness, echogenity and pulsatility index (PI) of uterine artery were evaluated in the late proliferative, early and mid secretory phase. The same sonographic examination was performed in the artifi cial cycle with oral estrogen-progesterone substitution used for endometrial preparation for transfer of cryopreserved-thawed embryos. Results: In the late proliferative phase of the natural cycle the thickness of endometrium was higher than in the artefi cial cycle (p=0.05). Triple-line echogenity prevailed in both cycles. The PI in natural cycle was lower (p=0.01) on the side of the growing Graafi an follicle compared to the other side and lower (p=0.05) than in the artifi cial cycle. In the secretory phase there were no differences in endometrial thickness within cycles. Homogenous hyperechoic endometrium interprevailed in both cycles and the lowest PI was found on the 7th day both after ovulation and after initiation of progesterone substitution. Conclusion: Progesterone addition after endometrial preparation with estrogen should be instituted when the endometrium thickness reached at least 9 mm and isoechoic or triple line echogenity is found.

        Key words: oral estrogen-progesterone substitution, endometrial thickness, endometrial echogenity, pulsatility index of uterine artery