Triggering ovulation at smaller versus larger follicle sizes in a modified natural cycle
Triggering Ovulation at Follicle Size Smaller or Larger Than 17mm in a Modified Natural Cycle
This trial tests whether triggering ovulation when follicles are 13–16.9 mm works as well as triggering at 17–22 mm for people having a modified natural cycle frozen embryo transfer.
Quick facts
| Phase | Not applicable |
|---|---|
| Study type | Interventional |
| Enrollment | 572 (estimated) |
| Ages | 18 Years to 50 Years |
| Sex | Female |
| Sponsor | Vida Recoletas Sevilla Academic / other |
| Locations | 1 site (Seville, Sevilla) |
| Trial ID | NCT07088952 on ClinicalTrials.gov |
What this trial studies
This is a prospective randomized non-inferiority trial comparing ovulation triggers at follicle diameters of 13–16.9 mm versus the conventional 17–22 mm in a modified natural cycle (mNC) frozen embryo transfer (FET) setting. Eligible participants have spontaneous menstrual cycles, at least one expanded blastocyst, and consent to mNC FET, while those with abnormal uterine cavity or intrauterine fluid are excluded. Participants are randomized to early or standard follicle-size trigger groups and followed for implantation and pregnancy outcomes to compare reproductive success. The study seeks to determine if earlier triggering preserves pregnancy rates while increasing scheduling flexibility for clinics and patients.
Who should consider this trial
Good fit: Ideal candidates are people with regular spontaneous cycles planning an mNC frozen embryo transfer who have at least one expanded blastocyst and no uterine cavity abnormalities.
Not a fit: People with abnormal uterine cavities, endometrial fluid, irregular or suppressed cycles, or those requiring hormone replacement endometrial preparation are unlikely to benefit from this protocol.
Why it matters
Potential benefit: If successful, this approach could allow clinics and patients to schedule FETs more flexibly without reducing pregnancy success.
How similar studies have performed: Some smaller studies and clinic reports suggest flexibility in mNC timing may be safe, but randomized non-inferiority data specifically comparing 13–16.9 mm versus 17–22 mm triggers are limited.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * At least one expanded blastocyst (regardless of its quality) * Spontaneous menstrual cycles * Consent to undergo frozen embryo transfer in a modified natural cycle Exclusion Criteria: * Abnormal uterine cavity * Fluid in endometrial cavity
Where this trial is running
Seville, Sevilla
- Vida Recoletas Sevilla — Seville, Sevilla, Spain (Recruiting)
Study contacts
- Study coordinator: Manuel Fernández Sánchez, MD PhD
- Email: vida.investiga@gruporecoletas.com
- Phone: +34954286274
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.