A Reduction in Intraovarian Arterial Blood Flow Resistance After Ovulation is Necessary to Achieve Pregnancy in Natural Cycle

Abstract

Color Doppler imaging permits the accurate localization of vessels and high-frequency pulsed Doppler ultrasonography has improved the resolution of flow velocity waveforms. In this study, intraovarian arterial blood flow before and after follicle rupture in the natural cycle was examined using transvaginal color flow Doppler imaging and changes in intraovarian arterial resistance in relation to the outcome of infertility treatment was analyzed. In a prospective study, 227 spontaneous cycles in 118 infertile patients who were undergoing infertility treatment at the division of Reproductive Medicine in our center were recruited in this study. The impedance to flow in intraovarian vessels was measured by means of transvaginal color flow Doppler imaging during the periovulatory period in the natural cycle of all patients. The pulsatility index (PI) of intraovarian arterial blood flow and pregnancy rate was evaluated. On the basis of PI values before and after follicular rupture, 227 cycles were classified into severely decreased (113 cycles) and not-severely decreased groups (114 cycles). The pregnancy rate per cycle in the severely decreased group was 18.6% (21/113), significantly higher than that in the not-severely decreased group (7/114; 6.1%, p = 0.004). The miscarriage rate was similar in the two groups. A reduction in intraovarian blood vessel resistance is necessary to achieve pregnancy in a natural cycle.