P-418: Changes in blood flow in the human corpus luteum throughout the menstrual cycle and during early pregnancy

Abstract

Angiogenesis is important for development of the corpus luteum and maintenance of luteal function. To maintain progesterone production for successful pregnancy, especially when the corpus luteum is rescued by pregnancy, not only high vascularization but also adequate blood flow in the corpus luteum are necessary to provide luteal cells with large amounts of cholesterol needed for progesterone synthesis and for the delivery of progesterone to the circulation. The present study was undertaken to investigate the change in blood flow in the human corpus luteum throughout the menstrual cycle and during early pregnancy. A prospective observational study. Ninety patients with normal menstrual cycles and normal luteal function were recruited in this study. Blood flow impedances were examined in the preovulatory follicle (late follicular phase) and in the corpus luteum throughout the luteal phase (early stage of the early luteal phase:1-2 days after ovulation [D1-2], late stage of the early luteal phase:D3-4, mid-luteal phase:D5-8, late luteal phase:D10-14). Transvaginal color and pulsed Doppler ultrasound was used to evaluate perifollicular and luteal arterial blood flow and blood flow impedance was expressed as resistance index (RI). Venous blood for progesterone concentration was taken on the day of the Doppler exam during the mid-luteal phase. Eleven patients who had low serum progesterone concentrations (< 10ng/ml) in the mid-luteal phase (luteal phase defect) and 17 patients who achieved pregnancy were also recruited in this study, and their blood flow impedance were examined. RI in the preovulatory follicle decreased after ovulation. Then RI in the corpus luteum further decreased from the early stage to the late stage during the early luteal phase. RI in the corpus luteum of the mid-luteal phase was the same level as the late stage of the early luteal phase. RI in the corpus luteum thereafter increased in the late luteal phase but remained low until 7weeks of gestation during early pregnancy. A highly negative correlation was observed between the RI of the corpus luteum and serum progesterone concentrations in the mid-luteal phase. RI of the patient with luteal phase defect was significantly higher than that of the patient with normal luteal function. The present study showed the change in luteal blood flow throughout the menstrual cycle and during early pregnancy. The changes in luteal blood flow well reflect luteal angiogenesis during the formation of the corpus luteum and blood vessel regression during the corpus luteum regression. Furthermore, the present study suggests that luteal blood flow is closely associated with luteal function.