An observational study in Infertility, Female, sponsored by Clinique Mathilde. Completed at 1 site in France. Open to female participants aged 18 Years to 45 Years. Per ClinicalTrials.gov, last updated 2026-03-04.
Sponsored by Clinique Mathilde · Observational
This retrospective study included 1,831 single blastocyst frozen embryo transfer (FET) cycles performed between November 1, 2022 and August 31, 2025. Three endometrial preparation protocols were used according to ovulatory status, cycle duration, and characteristics of previous FET cycles: modified natural cycle with ovulation trigger (mNC-FET) (n = 770), stimulated cycle FET (SC-FET) (n = 468), and hormone replacement therapy FET (HRT-FET) (n = 593). In natural cycles, if the predefined criteria for ovulation trigger were not met, the cycle was converted to a stimulated cycle. The aim of this study was to determine whether body mass index affects embryo transfer feasibility, reproductive outcomes, and cycle characteristics across different FET protocols.
540 studies on the registry are indexed under Infertility, Female; 138 are open to participants now.
This study's enrollment of 1,831 is above the median of 171 across 158 observational studies indexed under Infertility, Female.
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Women undergoing assisted reproductive technology (ART) with frozen embryo transfer (FET) at a tertiary fertility center were retrospectively identified. The study population included adult patients who underwent endometrial preparation using one of the following protocols: modified natural cycle with ovulation trigger, stimulated cycle, or hormone replacement therapy (HRT). Participants were categorized according to body mass index (BMI) into obese and non-obese groups for comparative analysis of embryo transfer feasibility and reproductive outcomes.
Women aged ≥18 years at the time of frozen embryo transfer.
Patients undergoing assisted reproductive technology (ART) with frozen embryo transfer (FET) using a natural, modified natural, stimulated, or hormone replacement therapy (HRT) protocol.
Availability of body mass index (BMI) measurement prior to initiation of the treatment cycle.
Procedure: Modified natural cycle
Procedure: Substitued cycle
Procedure: Hormonal replacement therapy
In the modified natural cycle group, patients underwent ultrasound and hormonal monitoring to track spontaneous follicular development. When the leading follicle reached an appropriate size and endometrial thickness was adequate, ovulation was triggered using human chorionic gonadotropin (hCG) to schedule frozen embryo transfer.
In the stimulated cycle group, mild ovarian stimulation was performed using oral agents and/or low-dose gonadotropins to promote follicular development. Follicular growth was monitored by ultrasound, and ovulation was either triggered with hCG or occurred spontaneously, allowing scheduling of frozen embryo transfer.
In the hormone replacement therapy group, endometrial preparation was achieved through exogenous estrogen administration. Once adequate endometrial thickness was confirmed, progesterone supplementation was initiated to mimic the luteal phase and schedule frozen embryo transfer.
feasibility of embryo transfer
Proportion of treatment cycles in which the planned frozen embryo transfer (FET) was performed as scheduled, regardless of the number of embryos transferred.
Time frame: scheduled day of embryo transfer (Day 0 of planned FET cycle)
Clinical pregnancy
Presence of an intrauterine gestational sac with fetal cardiac activity confirmed by transvaginal ultrasound.
Time frame: 6 weeks after embryo transfer
Miscarriage rate
Pregnancy loss occurring after confirmation of clinical pregnancy and before 12 completed weeks of gestation.
Time frame: 12 weeks of gestation
Cycle cancellation rate
Proportion of initiated FET cycles in which embryo transfer was not performed due to inadequate endometrial development, ovulation disorder, premature luteinization, or other clinical reasons.
Time frame: scheduled day of embryo transfer
Conversion from natural to stimulated cycles
Proportion of cycles initially planned as natural or modified natural cycles that required initiation of ovarian stimulation due to insufficient follicular development or ovulatory dysfunction.
Time frame: time of treatment protocol modification during the stimulation phase (prior to ovulation trigger)
Plan to share: No
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This study is completed, as verified in Mar 2026. You cannot join it, but the record below documents what was studied.
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Clinique Mathilde