Vaginal ultrasound is recommended for monitoring ovulation because it is more accurate and has a higher resolution than abdominal ultrasound. And vaginal ultrasound does not need to hold urine, in the case of emptying the bladder to do the examination will see more clearly. The following patients need to detect ovulation: 1, patients with polycystic ovary syndrome, these patients have ovulation dysfunction and often have immature eggs, so ovulation can be detected to understand the function of the ovary. 2, patients taking ovulation stimulating drugs need to monitor ovulation, and there is also the need to detect ovulation for embryo transfer. Through the monitoring of ovulation to understand the maturity of the egg, can be carried out at the appropriate time to retrieve the eggs of the operation. 3, the preparation for pregnancy during the female can also monitor ovulation, because in the ovulation period of sexual intercourse, can improve the probability of conception.