Blood flow changes in the intraovarian arteries during the periovulatory period: relationship to the time of day.

Intraovarian blood flow was assessed by transvaginal color and pulsed Doppler ultrasound prospectively in six women during the periovulatory period. All patients had regular ovulatory menstrual cycles and a mid-luteal serum progesterone level consistent with spontaneous ovulation in the preceding cycle. Each patient underwent serial transvaginal ultrasound examination and Doppler assessment of blood flow in the ovarian stroma and in the wall of the dominant follicle or corpus luteum. When the mean follicular diameter was > 16 mm or day -2 from the estimated day of ovulation was reached, patients were scanned at 6-h intervals at 06.00, 12.00, 18.00 and 24.00 until follicular rupture, to investigate the presence of circadian rhythms. The pulsatility index (PI) and the maximum peak systolic blood flow velocity (Vmax) were calculated as Doppler indices of impedance to blood flow and velocity, respectively. A venous blood sample was taken at each visit for subsequent hormonal analysis. There was no significant circadian fluctuation in either mean follicular Vmax or mean follicular PI before or after the luteinizing hormone (LH) surge. Similarly, mean Vmax and mean PI in the non-dominant ovarian stroma did not show any significant fluctuation over the same periods. The mean PI in the dominant ovarian stroma showed daily fluctuations with the highest values occurring most commonly at 06.00 and the nadir in the afternoon and late evening. This fluctuation was the reverse of the circadian variation previously demonstrated in the uterine artery. However, in contrast to the uterine artery, comparison between the mean PI values in the dominant ovarian stroma at 06.00 and 18.00 only approached significance after the LH surge. The dominant ovarian stroma Vmax tended to rise during the day, although the differences between 06.00 and 18.00 were also not significant. Although there are fluctuations in Doppler blood flow indices in the dominant ovarian stroma, further studies are necessary to demonstrate whether this represents a significant circadian rhythm.