Ipsilateral versus contralateral ovary selection of dominant follicle in succeeding cycle

There is still confusion as to whether ovulation in a succeeding cycle is a random event or is more likely to occur at the ipsilateral or contralateral ovary. Both histologic and sonographic data support alternating ovulation. Some ultrasound studies have suggested that ipsilateral ovulation is more likely in succeeding cycles, and another found right-sided ovulation to be more common. Because many of the studies are based upon small numbers, we initiated a large study to determine the more likely side of ovulation. Furthermore, the present investigation attempted to confirm biochemically the true existence of the dominant follicle by demonstrating appropriate serum estradiol levels. Evaluation of natural cycles (286 pairs) demonstrated 52.4% ipsilateral ovulation and 47.6% contralateral ovulation. Right-sided ovulation occurred in 54.5% of cycles. Our data suggest that the side of ovulation in successive cycles is not influenced by the side of ovulation in the preceding cycle.