Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial

Clara Colombo; Amalie Johansen Somuncu; Marte Saupstad; Sara Johanna Bergenheim; Tine Vrist Dam; Nathalie Friis Wang; Birgitte Oxlund-Mariegaard; Ellen Løkkegaard; Merete Husth; Mette Petri Lauritsen; Julie Lyng Forman; Nina La Cour Freiesleben; Bugge Nøhr; Kristine Løssl; Anja Pinborg

doi:10.61409/A03250214

Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial

Clara Colombo^*, Amalie Johansen Somuncu, Marte Saupstad, Sara Johanna Bergenheim, Tine Vrist Dam, Nathalie Friis Wang, Birgitte Oxlund-Mariegaard, Ellen Løkkegaard, Merete Husth, Mette Petri Lauritsen, Julie Lyng Forman, Nina La Cour Freiesleben, Bugge Nøhr, Kristine Løssl, Anja Pinborg

^*Corresponding author for this work

Abstract

INTRODUCTION: It is standard clinical practice to postpone frozen embryo transfer (FET) for at least one menstrual cycle after a failed fresh embryo transfer or a freeze-all cycle. Delaying FET has been hypothesised to minimise the negative effect of controlled ovarian stimulation. However, this practice may be associated with increased psychological distress and delayed time to pregnancy. In this clinical study, we aim to investigate whether immediate SC- or PC-FET is non-inferior to postponed SC- and PC-FET in terms of live birth rate (LBR).

METHODS: The study is designed as a multicentre, randomised controlled, non-blinded, non-inferiority trial. A total of 484 women aged 18-45 years who are set to undergo SC- or PC-FET will be included in the trial. Participants will be randomised 1:1 to FET in the first cycle after a failed fresh transfer or freeze all (FET immediate) or to FET in a subsequent cycle (FET postponed). The main outcome will be LBR.

CONCLUSIONS: If immediate FET proves to be as efficient and safe as postponed FET, immediate FET offers various advantages, such as a shorter time to pregnancy for couples who did not conceive in the fresh cycle and lower expenses due to a shorter freezing time.

FUNDING: This work was supported by a research grant from Merck Denmark. Merck Denmark was in no way involved in the design of the study and will not be involved in the analysis or interpretation of results.

CLINICALTRIALS: gov (NCT06304792).

Original language	English
Article number	A03250214
Journal	Danish Medical Journal
Volume	72
Issue number	8
ISSN	1603-9629
DOIs	https://doi.org/10.61409/A03250214
Publication status	Published - 22 Jul 2025

Keywords

Humans
Female
Embryo Transfer/methods
Pregnancy
Adult
Cryopreservation
Pregnancy Rate
Adolescent
Young Adult
Ovulation Induction/methods
Middle Aged
Live Birth
Time Factors
Randomized Controlled Trials as Topic
Time-to-Pregnancy
Birth Rate

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Colombo, C., Somuncu, A. J., Saupstad, M., Bergenheim, S. J., Dam, T. V., Wang, N. F., Oxlund-Mariegaard, B., Løkkegaard, E., Husth, M., Lauritsen, M. P., Forman, J. L., Freiesleben, N. L. C., Nøhr, B., Løssl, K., & Pinborg, A. (2025). Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial. Danish Medical Journal, 72(8), Article A03250214. https://doi.org/10.61409/A03250214

Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial. / Colombo, Clara ; Somuncu, Amalie Johansen; Saupstad, Marte et al.
In: Danish Medical Journal, Vol. 72, No. 8, A03250214, 22.07.2025.

Research output: Contribution to journal › Journal article › Research › peer-review

Colombo, C , Somuncu, AJ, Saupstad, M, Bergenheim, SJ, Dam, TV , Wang, NF, Oxlund-Mariegaard, B, Løkkegaard, E, Husth, M, Lauritsen, MP, Forman, JL, Freiesleben, NLC , Nøhr, B , Løssl, K & Pinborg, A 2025, 'Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial', Danish Medical Journal, vol. 72, no. 8, A03250214. https://doi.org/10.61409/A03250214

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title = "Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial",

abstract = "INTRODUCTION: It is standard clinical practice to postpone frozen embryo transfer (FET) for at least one menstrual cycle after a failed fresh embryo transfer or a freeze-all cycle. Delaying FET has been hypothesised to minimise the negative effect of controlled ovarian stimulation. However, this practice may be associated with increased psychological distress and delayed time to pregnancy. In this clinical study, we aim to investigate whether immediate SC- or PC-FET is non-inferior to postponed SC- and PC-FET in terms of live birth rate (LBR).METHODS: The study is designed as a multicentre, randomised controlled, non-blinded, non-inferiority trial. A total of 484 women aged 18-45 years who are set to undergo SC- or PC-FET will be included in the trial. Participants will be randomised 1:1 to FET in the first cycle after a failed fresh transfer or freeze all (FET immediate) or to FET in a subsequent cycle (FET postponed). The main outcome will be LBR.CONCLUSIONS: If immediate FET proves to be as efficient and safe as postponed FET, immediate FET offers various advantages, such as a shorter time to pregnancy for couples who did not conceive in the fresh cycle and lower expenses due to a shorter freezing time.FUNDING: This work was supported by a research grant from Merck Denmark. Merck Denmark was in no way involved in the design of the study and will not be involved in the analysis or interpretation of results.CLINICALTRIALS: gov (NCT06304792).",

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author = "Clara Colombo and Somuncu, \{Amalie Johansen\} and Marte Saupstad and Bergenheim, \{Sara Johanna\} and Dam, \{Tine Vrist\} and Wang, \{Nathalie Friis\} and Birgitte Oxlund-Mariegaard and Ellen L{\o}kkegaard and Merete Husth and Lauritsen, \{Mette Petri\} and Forman, \{Julie Lyng\} and Freiesleben, \{Nina La Cour\} and Bugge N{\o}hr and Kristine L{\o}ssl and Anja Pinborg",

note = "Published under Open Access CC-BY-NC-BD 4.0. https://creativecommons.org/licenses/by-nc-nd/4.0/.",

year = "2025",

month = jul,

day = "22",

doi = "10.61409/A03250214",

language = "English",

volume = "72",

journal = "Danish Medical Journal",

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T1 - Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial

AU - Colombo, Clara

AU - Somuncu, Amalie Johansen

AU - Saupstad, Marte

AU - Bergenheim, Sara Johanna

AU - Dam, Tine Vrist

AU - Wang, Nathalie Friis

AU - Oxlund-Mariegaard, Birgitte

AU - Løkkegaard, Ellen

AU - Husth, Merete

AU - Lauritsen, Mette Petri

AU - Forman, Julie Lyng

AU - Freiesleben, Nina La Cour

AU - Nøhr, Bugge

AU - Løssl, Kristine

AU - Pinborg, Anja

N1 - Published under Open Access CC-BY-NC-BD 4.0. https://creativecommons.org/licenses/by-nc-nd/4.0/.

PY - 2025/7/22

Y1 - 2025/7/22

N2 - INTRODUCTION: It is standard clinical practice to postpone frozen embryo transfer (FET) for at least one menstrual cycle after a failed fresh embryo transfer or a freeze-all cycle. Delaying FET has been hypothesised to minimise the negative effect of controlled ovarian stimulation. However, this practice may be associated with increased psychological distress and delayed time to pregnancy. In this clinical study, we aim to investigate whether immediate SC- or PC-FET is non-inferior to postponed SC- and PC-FET in terms of live birth rate (LBR).METHODS: The study is designed as a multicentre, randomised controlled, non-blinded, non-inferiority trial. A total of 484 women aged 18-45 years who are set to undergo SC- or PC-FET will be included in the trial. Participants will be randomised 1:1 to FET in the first cycle after a failed fresh transfer or freeze all (FET immediate) or to FET in a subsequent cycle (FET postponed). The main outcome will be LBR.CONCLUSIONS: If immediate FET proves to be as efficient and safe as postponed FET, immediate FET offers various advantages, such as a shorter time to pregnancy for couples who did not conceive in the fresh cycle and lower expenses due to a shorter freezing time.FUNDING: This work was supported by a research grant from Merck Denmark. Merck Denmark was in no way involved in the design of the study and will not be involved in the analysis or interpretation of results.CLINICALTRIALS: gov (NCT06304792).

AB - INTRODUCTION: It is standard clinical practice to postpone frozen embryo transfer (FET) for at least one menstrual cycle after a failed fresh embryo transfer or a freeze-all cycle. Delaying FET has been hypothesised to minimise the negative effect of controlled ovarian stimulation. However, this practice may be associated with increased psychological distress and delayed time to pregnancy. In this clinical study, we aim to investigate whether immediate SC- or PC-FET is non-inferior to postponed SC- and PC-FET in terms of live birth rate (LBR).METHODS: The study is designed as a multicentre, randomised controlled, non-blinded, non-inferiority trial. A total of 484 women aged 18-45 years who are set to undergo SC- or PC-FET will be included in the trial. Participants will be randomised 1:1 to FET in the first cycle after a failed fresh transfer or freeze all (FET immediate) or to FET in a subsequent cycle (FET postponed). The main outcome will be LBR.CONCLUSIONS: If immediate FET proves to be as efficient and safe as postponed FET, immediate FET offers various advantages, such as a shorter time to pregnancy for couples who did not conceive in the fresh cycle and lower expenses due to a shorter freezing time.FUNDING: This work was supported by a research grant from Merck Denmark. Merck Denmark was in no way involved in the design of the study and will not be involved in the analysis or interpretation of results.CLINICALTRIALS: gov (NCT06304792).

KW - Humans

KW - Female

KW - Embryo Transfer/methods

KW - Pregnancy

KW - Adult

KW - Cryopreservation

KW - Pregnancy Rate

KW - Adolescent

KW - Young Adult

KW - Ovulation Induction/methods

KW - Middle Aged

KW - Live Birth

KW - Time Factors

KW - Randomized Controlled Trials as Topic

KW - Time-to-Pregnancy

KW - Birth Rate

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U2 - 10.61409/A03250214

DO - 10.61409/A03250214

M3 - Journal article

C2 - 40747727

SN - 1603-9629

VL - 72

JO - Danish Medical Journal

JF - Danish Medical Journal

IS - 8

M1 - A03250214

ER -

Immediate versus postponed blastocyst transfer in stimulated or programmed frozen embryo transfer cycles - a protocol for a non-blinded randomised clinical trial

Abstract

Keywords

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