What is a follicle study, and why do I need so many scans in one cycle?

A follicle study (also called follicular monitoring or ovulation tracking) is a series of transvaginal ultrasound scans across one cycle. A follicle is the small fluid-filled sac in the ovary that holds a developing egg. The scans let the doctor see whether a follicle is growing, roughly how fast, and when it is likely to release the egg. At each scan they usually measure the size of the leading follicle or follicles and the thickness and pattern of the uterine lining. A follicle typically grows a couple of millimetres a day and often ovulates somewhere around 18 to 24 mm, though this varies. A later scan may show that the follicle has collapsed, suggesting ovulation has happened. This information is used to time intercourse or IUI, to decide if and when to give a trigger injection, and to check how you respond to ovulation medicines, including whether too many follicles are growing. Scan dates are adjusted based on what is seen, which is why the number of visits can change. The scans are generally quick and painless, though slightly uncomfortable for some. Ask the doctor to tell you the follicle size and lining thickness each time and what the plan is for the next visit.