Ovulation monitoring is a relatively simple way to help pregnancy, which means that the doctor will do an ultrasound examination to observe the development of follicles in the ovaries and combine it with urine LH or blood hormone tests to predict the ovulation date more accurately, so as to guide the timing of intercourse and improve the chance of conception. So, when is the right time to start ovulation monitoring, since it will miss the ovulation time and starting too early will increase the number of visits? First of all, we need to clarify the concept that the menstrual cycle is usually referred to as the number of days between the first day of the first menstrual period and the first day of the next menstrual period, which is called the duration of a menstrual cycle, usually 28-30 days. Many people mistakenly think that it is the time from the first day of menstruation to the next day of menstruation, but this is not true; the first day of menstruation that doctors usually tell us is also the first day of menstruation, not the first day of menstruation. We need to clarify this concept. In clinical practice, when we talk about when ovulation monitoring starts, we are also referring to the first day of menstrual bleeding, not how long after menstruation. Next, let’s look at the process of follicular development under normal circumstances. See the diagram below: In a 28-day menstrual cycle, for example, the follicle development period is the first 14 days after the start of menstruation, and it is usually more appropriate to perform follicle monitoring around the 10th day of menstruation. However, everyone’s menstrual cycle is different. If the menstrual cycle is shorter than 28 days, the first follicle monitoring should be done 1-2 days earlier; if the menstrual cycle is longer than 28 days, the first follicle monitoring can be done 1-2 days longer. Since the doctor will guide the woman for the next follow-up visit based on the results of the first follicle monitoring, it is better to have the first follicle monitoring earlier rather than later, as there are sometimes abnormalities such as small follicles ovulation and delayed follicle development in the clinic.