It is a series of transvaginal ultrasound scans that monitors the entire growth process of a follicle from the start of the menstrual cycle to the release of an egg. It forms a vital part of fertility treatments. It helps doctors find out when the patient will ovulate and the number of mature eggs that will ovulate. It also helps to find out the thickness of the Uterine Lining. Ultrasound monitoring also allows the doctor to determine how a woman responds to fertility medication.