thanks for asking in Healthcare Magic.
Inadequate Gonadotropin secretion causes infertility
. Gonadotropins are given to induce ovulation. Both Menptropin and Fostimon are extracted and purified from urine of post menopausal women.
Menopur is Menotropin and Fostimon is Urofolitropin. Menotropin contains both Follicle Stimulating Hormone
(FSH) and Luteinising homone (LH). Urofolitropin contains only FSH. In persons with elevated LH/FSH ratio as in poly cystic ovarian disease
(PCOD), Urofolitropin is preferred.
Urofolitropin is is claimed to improve the chances of obtaining good quality ova for in vitro fertilization
Menotropin induces simultaneous maturation of several ova and also precisely times the ovulation to facilitate their harvesting for in vitro fertilization. Menotropin injection daily for 10 days followed by Human Chorionic Gonadotropin
(HCG) can induce ovulation within 24 to 48 hours in 75% of persons.Since you are nearing 40 the chances of ovulation will be better with Menotropin and the Dr is right in switching over from Fostimon to Menopur.
I hope this is useful to you.