Precise day of ovulation determined by real-time ultrasound evidence of graafian follicular development

Real-time ultrasonic scanning was performed in 21 infertile Japanese women during 37 menstrual cycles. The maximum diameter prior to ovulation was 23.3 +/- 2.9 mm in spontaneous ovulation cycles, 29.6 +/- 5.2 mm in case of clomiphene therapies, and 26.7 +/- 3.9 mm in HMG-HCG therapies, respectively. Size of the graafian follicles was maximum at almost the same time as the LH peak in the plasma and urine, respectively. The LH peak in the urine was determined by the hemagglutination inhibition assay, the results of which were obtainable within 2 h. Four patients became pregnant (19.0%). There was no statistical correlation between the diameter of the largest follicle and the plasma estradiols (r = 0.28, 0.2 less than P less than 0.3) or between the diameter of the largest follicle and the peak luteinising hormone level (r = 0.27, 0.3 less than P less than 0.4). Therefore, the combination of the real-time ultrasound and a hemagglutination inhibition assay for LH in urine can be clinically applied to detect the precise day of the ovulation.