TY - JOUR

T1 - The future of frozen-thawed embryo transfer in hormone replacement therapy cycles

AU - Løssl, Kristine

AU - Spangmose, Anne Lærke

AU - Asserhøj, Louise Laub

AU - Dam, Tine Vrist

AU - Pinborg, Anja

N1 - Publisher Copyright: © 2023 Lippincott Williams and Wilkins. All rights reserved.

PY - 2023

Y1 - 2023

N2 - Purpose of reviewThis review focuses on the efficacy of letrozole stimulated frozen-thawed embryo transfer (FET) compared to hormone replacement therapy (HRT) FET in women with polycystic ovarian syndrome (PCOS) and/or oligo-anovulation. Further, obstetric and perinatal risks in HRT FET are summarized.Recent findingsThe presence of a corpus luteum seems to reduce the risk of pregnancy-related hypertension and preeclampsia after FET. As a natural cycle (NC) FET is not an option for women with oligo-/amenorrhea these women may benefit from FET with mild stimulation compared to HRT FET. The intention of mild stimulation in anovulatory women is to induce (mono) ovulation to mimic the endocrine profiles of the natural cycle and the early pregnancy after natural conception. Mild stimulation by letrozole is patient friendly and cheap compared to gonadotropin stimulated FET and has been increasingly used in recent years. Although the quality of evidence is low, the pregnancy outcomes after letrozole FET seems similar or even better compared to HRT FET in women with PCOS and/or oligo-anovulation.SummaryNatural and modified NC FET should be used whenever possible to mitigate adverse obstetric and perinatal outcomes after HRT FET. For anovulatory women, whenever ovulation can be induced, we advocate the use of mild stimulation FET to create a corpus luteum awaiting results from RCTs limited to oligo-anovulatory women.

AB - Purpose of reviewThis review focuses on the efficacy of letrozole stimulated frozen-thawed embryo transfer (FET) compared to hormone replacement therapy (HRT) FET in women with polycystic ovarian syndrome (PCOS) and/or oligo-anovulation. Further, obstetric and perinatal risks in HRT FET are summarized.Recent findingsThe presence of a corpus luteum seems to reduce the risk of pregnancy-related hypertension and preeclampsia after FET. As a natural cycle (NC) FET is not an option for women with oligo-/amenorrhea these women may benefit from FET with mild stimulation compared to HRT FET. The intention of mild stimulation in anovulatory women is to induce (mono) ovulation to mimic the endocrine profiles of the natural cycle and the early pregnancy after natural conception. Mild stimulation by letrozole is patient friendly and cheap compared to gonadotropin stimulated FET and has been increasingly used in recent years. Although the quality of evidence is low, the pregnancy outcomes after letrozole FET seems similar or even better compared to HRT FET in women with PCOS and/or oligo-anovulation.SummaryNatural and modified NC FET should be used whenever possible to mitigate adverse obstetric and perinatal outcomes after HRT FET. For anovulatory women, whenever ovulation can be induced, we advocate the use of mild stimulation FET to create a corpus luteum awaiting results from RCTs limited to oligo-anovulatory women.

KW - frozen embryo transfer

KW - hormone replacement therapy

KW - letrozole

KW - live birth rate

KW - preeclampsia

U2 - 10.1097/GCO.0000000000000867

DO - 10.1097/GCO.0000000000000867

M3 - Review

C2 - 37185352

AN - SCOPUS:85158021931

VL - 35

SP - 200

EP - 209

JO - Current Opinion in Obstetrics and Gynecology

JF - Current Opinion in Obstetrics and Gynecology

SN - 1040-872X

IS - 3

ER -