Triggering Ovulation at Follicle Size Smaller or Larger Than 17mm in a Modified Natural Cycle

Recruiting now · Not applicable

Conditions studied: Embryo Transfer

In brief

The rise in frozen embryo transfer (FET) cycles within assisted reproductive technology (ART) has sparked the need to refine endometrial preparation protocols. The switch from hormone replacement cycles (HRT) to natural cycles, poses scheduling challenges onto laboratories, doctors and patients. The modified natural cycle (mNC), offering more precision for scheduling, shows promise but lacks comprehensive data on the potential flexibility of triggering criteria that may allow to control timing in a wider range. This prospective randomized study seeks to address this knowledge gap by evaluating the non-inferiority of triggering ovulation in mNC with follicle diameters of 13-16.9mm compared to the conventional 17-22mm. The study aims to enhance the understanding of the impact of follicle size at ovulation in reproductive outcomes, optimize FET treatments providing a more flexible mNC protocol, and improve patient care in ART clinics.

Key facts

Study ID

NCT07088952

Run by

Vida Recoletas Sevilla

People needed

572

Starts

2025-10-22

Expected to finish

2028-05-30

Last updated by the study team

2026-01-13

Who can join

Age: 18 and older, up to 50. Sex: female. Healthy volunteers: not accepted.

You may qualify if…

• At least one expanded blastocyst (regardless of its quality)
• Spontaneous menstrual cycles
• Consent to undergo frozen embryo transfer in a modified natural cycle

You may not qualify if…

• Abnormal uterine cavity
• Fluid in endometrial cavity

Where it is running

• Vida Recoletas Sevilla — Seville, Sevilla, Spain (enrolling)

Full record on ClinicalTrials.gov

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