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

Launched by VIDA RECOLETAS SEVILLA · Jul 24, 2025

Keywords

ClinConnect Summary

This clinical trial is studying the best time to trigger ovulation (the release of an egg) during a modified natural cycle for women undergoing frozen embryo transfer, a common treatment in fertility care. Usually, doctors wait until the follicle (the small sac that holds the egg) reaches a size between 17 and 22 millimeters before triggering ovulation. This study wants to see if triggering ovulation a little earlier, when the follicle is between 13 and 16.9 millimeters, works just as well. The goal is to make the timing of embryo transfers more flexible and convenient for patients and clinics without lowering the chances of pregnancy.

Women who have regular menstrual cycles, at least one good quality embryo frozen and ready for transfer, and who agree to undergo frozen embryo transfer in a modified natural cycle may be eligible for this study. Participants will be closely monitored, including ultrasounds to check follicle size and hormone levels, and will follow the modified natural cycle protocol where ovulation is triggered based on follicle size. The study excludes women with certain uterine conditions or hormone levels that could affect the results. This research could help improve fertility treatments by offering a more flexible and patient-friendly approach to timing embryo transfers.

Gender

FEMALE

Eligibility criteria

• Inclusion Criteria:
• • At least one expanded blastocyst (regardless of its quality)
• • Regular menstrual cycles (24-32 days)
• • Consent to undergo frozen embryo transfer in a modified natural cycle
• Exclusion Criteria:
• • Abnormal uterine cavity
• • Fluid in endometrial cavity
• • Endometrial thickness under 7mm on trigger day
• • Serum progesterone over 1.5 ng/ml on trigger day