Cycle management in frozen embryo transfer: the best of all worlds?

Abstract

A comprehensive review of the current literature was conducted to examine the available endometrial preparation methods prior to frozen embryo transfer (FET), and their impact on pregnancy outcomes and obstetric complications. Endometrial preparation for FET can be broadly categorized into natural and artificial cycles. While artificial cycles have historically been favoured for their flexibility, natural cycles are increasingly preferred due to their association with lower rates of obstetric and neonatal complications. However, in patients lacking ovarian function (e.g. menopausal women or those with premature ovarian insufficiency), artificial cycles remain the only viable option, necessitating further optimization. Flexibility within natural cycles can be achieved by varying the timing of ovulation induction or luteal phase initiation. Additionally, individualized luteal phase support with tailored progesterone supplementation is becoming standard practice in both natural and artificial cycles. Natural cycle FET is associated with fewer obstetric complications, and should be prioritized in patients with intact ovarian function. Further optimization of preparation protocols can be achieved through adequate follicular phase monitoring and personalized luteal phase support.