Ovarian stimulation is initiated during the 2 or 3 day of the menstrual cycle, after doing a baseline ultrasonography to look for thin endometrium (2-4mm) and rule out any follicles of more than 9mm (ideal size is 2-9 mm), biochemical tests like serum E2 levels (should be less than 25pg/ml ) and LH levels (should be less than 4-5IU/L) are done to look for down regulation.
Gonadotrophins in doses of 225 IU to 300 IU are given intramuscularly for 6-7 days, Under the influence of stimulating hormones multiple enlarging follicles can be seen rather than single dominant follicle created during natural menstrual cycle.
Follicles are monitored every alternate days depending on the response starting from day 7 of the menstrual cycle.
By the sonographic appearance of follicles from days 7-10 in combination with serum estradiol hormone levels we can predict the most likely time of ovulation.
Once the follicles have reached the optimal size and number (more than or equal to 2 follicles over 18 mm) for IVF the patient is given intramuscular inj HCG/recombinant HCG/GnRH agonists to trigger ovulation.
Careful planning of this stage permits optimal timing of oocyte retrieval for IVF.
Depending on the cause of infertility the number of follicles recruited may vary reaching up to 20 ,with ovulation carefully triggered when 40% of the follicles are 19-20 mm or greater in diameter .
For patients undergoing IVF, accurate timing of oocyte retrieval is critical. If done too early aspiration of the follicles will result in retrieval of immature oocytes and no successful fertilization .If done too late the oocytes will be spontaneously released into the peritoneal cavity and will be lost.