Infertility, Female
Conditions
Brief summary
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.
Interventions
PROCEDUREModified natural cycle
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.
PROCEDURESubstitued cycle
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.
PROCEDUREHormonal replacement therapy
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.
Sponsors
Clinique Mathilde
Study design
Observational model
COHORT
Time perspective
RETROSPECTIVE
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 45 Years
Healthy volunteers
No
Inclusion criteria
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| feasibility of embryo transfer | scheduled day of embryo transfer (Day 0 of planned FET cycle) | Proportion of treatment cycles in which the planned frozen embryo transfer (FET) was performed as scheduled, regardless of the number of embryos transferred. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Clinical pregnancy | 6 weeks after embryo transfer | Presence of an intrauterine gestational sac with fetal cardiac activity confirmed by transvaginal ultrasound. |
| Miscarriage rate | 12 weeks of gestation | Pregnancy loss occurring after confirmation of clinical pregnancy and before 12 completed weeks of gestation. |
| Cycle cancellation rate | scheduled day of embryo transfer | 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. |
| Conversion from natural to stimulated cycles | time of treatment protocol modification during the stimulation phase (prior to ovulation trigger) | 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. |
Countries
France
Outcome results
None listed