LAUSR

The hypothesis of the study was that the vascularity of ovulatory follicles (OF) determines the ovulatory status. The peri-follicular blood flow characteristics of OF were sequentially recorded using Color Doppler Imaging ultrasonography from the onset of induced estrus (Day 0) to ovulation at 12 h intervals. The OFs were categorized into two groups based on the timing of ovulation (i) Normal ovulation (OFN) - When ovulation occurred within 36 h after the onset of estrus (n = 18) and (ii) Delayed ovulation (OFD) - When ovulation occurred after 36 h (n = 15). The blood flow velocity, Doppler pulse duration (DPD) and Pulsatility index (PI) of the OF were recorded during each examination. The OF was well vascularized with a detectable blood flow signals, while the subordinate or atretic follicles were devoid of detectable blood flow. On Day 0, the DPD (874.33 ± 56.99 ms) and PI (0.62 ± 0.01) values were less in the OFN when compared to OFD (1140.56 ± 27.54 ms and 1.28 ± 0.15 respectively) group. In the OFD group, ovulation occurred between 36 and 60 h after onset of estrus when the DPD value reduced to 878.17 ms. Based on ROC analysis, it was evident that the DPD value of < 929 ms is a necessary factor for induction of ovulation. The decreased DPD and PI values of the OF on the day of estrus are positive indicators of a normal ovulation process.