The purpose of this study is to determine whether minimal ovarian stimulation for in vitro fertilization is superior to high dose stimulation. Number of mature eggs, number of embryos as well as pregnancy rates will be compared.

A prospective randomized trial will be carried out. The Minimal stimulation (MS) protocol is based on low dose letrozole 2.5 mg over 5 days, starting from cycle day 2, overlapping with low dose gonadotropins, starting from day 3 of the letrozole at 150 units per day. GnRH antagonist wil be introduced to avoid premature LH surge when one or more of the growing follicles reached approximately 14 mm in size. The high dose stimulation protocol is based on high dose of gonadotropins (≥300 IU/day) throughout the cycle with the usage of gonadotropin-releasing hormone (GnRH) antagonist to avoid premature luteinizing hormone (LH) surge as described above.

Inclusion Criteria:

• Clinical diagnosis of poor responder to ovarian stimulation

Exclusion Criteria:

• Patients undergoing pregestational diagnosis (PGD)
• Patients using donor eggs