If a woman is injected with human chorionic gonadotropin to promote ovulation, the follicle will usually rupture within 48 hours after the injection, prompting the egg to be discharged. However, because everyone’s physical condition is different and the diameter of the dominant follicle is uncertain before ovulation, the time can fluctuate to a certain extent. Therefore, after ovulation is stimulated by human chorionic gonadotropin, it is necessary to check the follicle in the ovary by ultrasound in about 24 hours. If ovulation is confirmed at the time of the examination, intercourse can be arranged in a timely manner, because the probability of conception within 36 hours after ovulation is very high. So the exact time of the follicle’s rupture and the time of the egg’s discharge need to be determined by the ultrasound examination.