Follicular monitoring or follicular study is important in assessing the ovarian follicles at regular intervals and documenting it for ovulation. Ultrasound monitoring is also done to know the ovarian volume, antral follicle number and ovarian stromal blood flow. Transvaginal ultrasound is preferred and the monitoring starts from the second day of menstrual periods. The number of existing follicles is counted and any other abnormality (such as polycystic ovaries) of the ovary is detected. Injections in IVF or Clomiphene tablets in IUI for stimulation are given and the patient is asked to come for the next visit. The patient comes for the monitoring after every two to three days and the stimulatory drugs are given based on the type of protocol decided. When the follicle size reaches the size of 18 mm to 21 mm hCG administration is done.