Ovarian morphology, endocrine function and intra-follicular blood flow during the peri-ovulatory period

Transvaginal ultrasonography with colour flow mapping has been used to study changes in intra-follicular morphology and blood flow during a peri-ovulatory period in one volunteer. Aspects of uterine morphology and blood flow were also recorded. The intervals from a defined luteinizing hormone (LH) rise and peak to the mean time of follicular rupture were 37.5 and 17.5 h, respectively. Blood flow velocity waveforms were observed clearly at the time of the LH rise and blood vessels were visible when the hormone level reached a peak. Concurrently, the wall of the follicle became less clear, crenated, thicker and more echogenic. A structure resembling the detached cumulus and oocyte was seen before the follicle had ruptured. Peak systolic blood velocity was highest immediately after ovulation had occurred. Blood flow impedance in the uterine arteries suggested the presence of a circadian rhythm, but no pronounced daily changes were observed over the study period. In contrast, flow velocity waveforms were clearly visible in the endometrium around the time of ovulation. These preliminary data suggest that intra-follicular vascularization or angiogenesis may be critical processes that might be used to predict ovulation and could possibly be modified to help achieve or avoid a pregnancy.