Letrozole for OHSS Prevention Post-IVF Pickup

Mechanism of Action and Clinical Application

Letrozole is an aromatase inhibitor that works by blocking the conversion of androgens to estrogen, thereby reducing peak estradiol levels during and after ovarian stimulation, which is the primary mechanism by which letrozole may prevent OHSS, as elevated estradiol levels are a key driver of increased vascular permeability and fluid shifts that characterize OHSS 1, 2

Letrozole does not compromise reproductive outcomes, with the number of mature oocytes retrieved remaining similar to conventional stimulation, fertilization capacity preserved, and clinical pregnancy rates comparable between letrozole and control groups 1, 2, 3
Letrozole does not increase the incidence of congenital abnormalities in offspring 3

For women with estrogen receptor-positive breast cancer undergoing fertility preservation, letrozole reduces peak estradiol levels to near-physiologic ranges while maintaining oocyte yield, and randomized trials show similar mature oocyte yields with letrozole-gonadotropin versus tamoxifen-gonadotropin protocols 2, 3, 4
Letrozole may be beneficial for patients with antiphospholipid antibodies or thrombophilia, as it yields lower peak estrogen levels, which may reduce thrombotic complications during ovarian stimulation 5