Follicular tracking or follicular study is a vital component of treatment. It basically employs a simple technique for assessing ovarian follicles at regular intervals most commonly done at DAY 10, DAY 12 and DAY 14 , sometimes another scan is done 2-3 days later to confirm ovulation.
Journey to ovulation begins during late luteal phase of prior menstrual cycle, when certain 2-5 mm sized healthy follicles form a population, from which dominant follicles is to be selected for next cycle This process is called 'recruitment'. Usual number of such follicles may be 5-15, which goes on decreasing with advancing age1.
This number can be reduced when a woman has had too many ovulation induction cycles, in premature ovarian failure or age more than 35 years
During Day 1-5 of the menstrual cycle, a second process of 'follicular selection' begins, when among all recruited follicles, certain growing follicles of size 5-10 mm are selected, while rest of the follicles regress or become atretic.
During Day 5-7 of the menstrual cycle, a process of 'dominance' begins, when a certain follicle of 10 mm size takes the control and becomes dominant. This follicle starts growing at rate of 2-3 mm a day and reaches 18-25 mm size just prior to ovulation. Process of dominance begins late, when suddenly a certain underdog follicle starts growing faster and suppresses others to become dominant".
Almost nearing ovulation, rapid follicle growth takes place, and follicle starts protruding from the ovarian cortex, attains a crenated border, and it literally explodes to release the ovum, along with some antral fluid to form a Corpus luteum.