Follicles 20 * 18mm, about 24 hours – 48 hours or so will be the case of ovulation, if you want to prepare for pregnancy by monitoring ovulation, at this time to actively coitus, it is recommended that the same night coitus, the next day and then coitus again, followed by ultrasound to monitor whether there is ovulation. Fertile women will develop a number of follicles in each menstrual cycle, after recruitment and selection, generally only one dominant follicle can be fully mature and discharge an egg. A follicle over 18mm in diameter is called a mature follicle, which means that it will ovulate within 24-48 hours. a follicle that is 20 x 18mm will often ovulate within 24 hours, and no later than 48 hours. However, there are individual differences in the exact time, and ultrasound testing of the follicles should be continued. At this time you can increase the frequency of intercourse, which can also increase the chances of pregnancy. If the symptoms of vaginal bleeding occur during ovulation, you should pay attention to rest, and at the same time, maintain pubic hygiene to avoid infection. You should strengthen physical exercise during the day to enhance resistance and immunity. If you want to prepare for pregnancy by monitoring ovulation, it is recommended to have active intercourse.