How long it takes for a follicle 15mm x 14mm to mature and expel an egg varies from person to person and needs to be analyzed on a case-by-case basis. Usually, the dominant follicle, also known as the mature follicle, may expel an egg when it reaches 22mm x 18mm in size. The current follicle size is 15mm x 14mm, if it can get normal development, it may take about 1-3 days to develop into a dominant follicle and then ovulate, but there are some individual differences in the specific time, and some people may not break the follicle that is not ovulate. It is recommended that you continue to visit your regular hospital gynecologist for ultrasound monitoring of follicle development. If you are of childbearing age and planning to get pregnant, you can arrange intercourse when the follicles reach 18mm in diameter and take oral folic acid tablets in advance to prevent fetal abnormalities.