Ovulation can occur in the morning or in the afternoon, due to individual differences, the specific time of ovulation can not be determined. Each menstrual cycle has the growth of follicles in the ovary, when the dominant follicle grows to 18~22mm it will break through the follicular membrane and expel the egg cells in it, this process is ovulation, the specific time of ovulation generally depends on the growth and development of the follicle, so the specific time can not yet be determined. For women who have the need to prepare for pregnancy, it is recommended that they use ovulation test paper to monitor ovulation or go to the gynecology department of a regular hospital to monitor follicular development under ultrasound, determine the time of ovulation according to the results of the examination, and then guide coitus to increase the chances of pregnancy, and at the same time pay attention to maintain a happy mood and do not overly nervous.