NCT07450300

Assessment of the Feasibility of Frozen Embryo Transfers in a Natural Cycle Among Obese Compared to Non-Obese Patients

• Status: Completed
• Phase: —
• Study type: Observational
• Enrollment: 1,831 (actual)
• Sponsor: Clinique Mathilde · Academic / Other
• Sex: Female
• Age: 18 Years – 45 Years
• Healthy volunteers: Not accepted

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.

Conditions

• Infertility, Female

Interventions

Type	Name	Description
PROCEDURE	Modified 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.
PROCEDURE	Substitued 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.
PROCEDURE	Hormonal 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.

Timeline

• Start date: 2022-11-01
• Primary completion: 2025-08-31
• Completion: 2026-01-31
• First posted: 2026-03-04
• Last updated: 2026-03-04

Locations

1 site across 1 country: France