Controlled ovarian hyper stimulation is a procedure in which the patient’s ovaries are stimulated for 10-12 days with hormone injections (gonadotrophins) in order to obtain the highest number of mature oocytes (eggs).The response to these injections is tracked by ultrasound, and after the cohort of follicles reaches 18-22mm (minimum 4-5), a trigger injection is administered, followed by ovum pickup (egg collection) 34-36 hours later.