Practical issues

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.

Inclusion Criteria:

• Age more than or equal to 18 and less than or equal to 40
• BMI more than or equal to 18 and less than or equal to 35
• Diagnosis of PCOS according to Rotterdam criteria
• Normal gynaecological ultrasound < 6 months before inclusion
• Signed informed consent form
• Day 5 or 6 frozen-thawed embryo transfer, blastocyst stage

Exclusion Criteria:

• Recurrent implantation failure
• Recurrent miscarriage
• Presence of adenomyosis
• Untreated intrauterine pathology
• rAFS (revised American Fertility Society) Grade III or IV endometriosis
• Hydrosalpinx
• In vitro maturation (IVM)
• Untreated autoimmune disorders
• (History of) malignancy
• Allergy or reaction to the use of progynova, utrogestan and/or letrozole in the past
• Pre-implantation genetic testing (PGT)

Sharing with other study site, UZ Gent