The growth rate of follicles is normally 1.5-2mm per day, as long as it is within the normal range, it is normal. So in the clinic, it should be noted that if it is to achieve the dominant state, you can choose to cohabit, clinically the chances of pregnancy will be improved, for example, when the follicle diameter reaches 18mm you can cohabit, basically the follicle diameter will rupture and exclude the egg in the case of reaching 20mm. In addition, the number of follicles in the clinic is still growing at a good rate, but some in the case of follicle diameter reaches 25mm, has not yet ruptured, in the clinic may be the follicle luteinization, in this case will not be pregnant, it is recommended that the clinic to find out the reasons for the cause, according to the cause and then give treatment, will improve the chances of pregnancy.