Letrozole for Polycystic Ovary Syndrome (LEFT Trial)

To offer patients with oligomenorrhoea or amenorrhoea an alternative to frozen embryo transfer in an artificial cycle, endometrial preparation using letrozole may be a valuable option. Letrozole, a potent, reversible nonsteroidal aromatase inhibitor with relatively short half-life, can successfully induce ovulation without any adverse anti-estrogenic effects and thus without affecting the endometrium. The use of letrozole typically results in monofollicular growth and this reduces the effect of supraphysiological levels of estrogen on the endometrium and embryo. The purpose of this study is to compare a frozen-thawed embryo transfer in an artificial cycle with a letrozole-induced ovulatory cycle, specifically in PCOS patients. The primary outcome is early pregnancy loss.