Vaginal blood flow during the menstrual cycle.

Six nulliparous young women slept 16 to 27 consecutive nights in a clinical research center. Vaginal blood flow was estimated from rates of removal of heat from the vaginal wall by a cooled probe inserted by the women immediately upon awakening. Plasma levels of estradiol, progesterone, luteinizing hormone, and follicle-stimulating hormone were determined. Measured also were vaginal temperature and systolic and diastolic blood pressures. Systematic changes during the cycle were detected for all variables except systolic blood pressure. Rising levels of estradiol during late follicular phase were not correlated significantly with vaginal blood flow rates.