Natural Frozen Embryo Transfer (FET) vs Substituted Frozen Embryo Transfer (FET)

In frozen embryo transfer substituted cycles, patients are treated with progesterone and estrogen in an attempt to mimic the natural cycle and a transfer is planned whenever the endometrium is ready. In contrast, in frozen embryo transfer natural cycle patients are not taking any hormones, only triggered with hCG (human chorionic gonadotropin) when a dominant follicle is ready or they wait for the disappearance of the dominant follicle to plan the transfer date. Some doctors and centres shift towards using the substituted protocol in an attempt to make scheduling easier with less frequent ultrasounds.

This study will aim to compare clinical and biochemical pregnancy rates in patients who underwent frozen embryo transfers in natural cycles vs substituted cycles at the centre.

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Key information

Conditions

Fertility Disorders

Age range

Up to 40 year

Sex eligibility

Female

Study type

Observational

Primary location

Clinique Ovo

Montreal, Quebec, H4P 2S4, Canada

Who can participate

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Age < 40 years old
Women having undergone either a frozen embryo transfer in natural cycle or substituted cycle
IVF and FET cycles done at Clinique OVO

Exclusion criteria

egg or embryo recipient
History of recurrent miscarriages, defined as ≥ 3 consecutive losses
Patients that needed Viagra, Plasma-Rich Platelet (PRP) or other modalities to improve their endometrial thickness
Uterine abnormalities
Abnormal hormonal profiles
FET Stimulated cycles
History of recurrent implantation failure defined as failed ≥ 2 euploid embryos transfer or ≥ 3 blastocysts

Treatment and study plan

Frozen embryo transfer

Other

A frozen embryo transfer involves thawing a fertilized embryo and transferring it in the uterus in order to obtain a pregnancy

Primary outcomes

Evaluate the clinical pregnancy rate of embryo transfer in natural vs substituted cycles

Time frame: 6 to 8 weeks after Frozen Embryo Transfer

clinical pregnancy is the presence of fetal heartbeat at the viability ultrasound

Sponsors and collaborators

Lead sponsor

Clinique Ovo

Industry

Registry information

Official study title

Embryo Transfer in Natural vs Substituted Cycle and the Scheduling Pattern of IVF

Important dates

Study start: 2023
Primary completion: 2023
Study completion: 2024
First posted: Sep 26, 2023
Registry last updated: Dec 9, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Published trials that share one or more normalized conditions with this study.

Completed