Best follicle size for triggering ovulation in women 35+ with low ovarian reserve (POSEIDON Group 4)
Official title: What Should Be The Optimal Ovulation Triggering Size in Poseidon Group 4 Patients Undergoing Ovarian Stimulation?
Run by Centrum Clinic IVF Center · NCT06433518 · Data updated 2026-11-12
This study will see if triggering ovulation when follicles measure 13–16 mm rather than waiting until >17 mm yields more mature eggs for women 35 and older with low ovarian reserve undergoing IVF.
Quick facts
| Study type | Observational |
|---|---|
| Ages | 35 Years to 44 Years |
| Sex | Women only |
| Enrollment | 200 (estimated) |
| Sponsor | Centrum Clinic IVF Center Academic / other |
| Locations | 1 site (Ankara, Ankara) |
| Status | Recruiting |
| Started | March 15, 2026 |
| Main results expected | December 1, 2026 |
| Study ends | December 30, 2026 |
| Registry record updated | March 19, 2026 |
| Trial ID | NCT06433518 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Women aged 35 or older who meet POSEIDON Group 4 criteria (AMH < 1.2 ng/mL and AFC < 5), undergoing controlled ovarian stimulation with short antagonist or long agonist protocols and maximum daily gonadotropin dose of 300 IU are ideal candidates.
✕Probably not a fit
Patients under 35, those with normal ovarian reserve, or those in natural/IVM/DuoStim/PGT cycles or with major untreated uterine pathology are unlikely to benefit from this comparison.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This is an observational comparison of two trigger-timing approaches in POSEIDON Group 4 IVF cycles in women aged 35 and above with low AMH and low AFC. Participants are grouped by trigger timing: an experimental group triggered at 13–16 mm and a control group triggered when follicles are >17 mm, with all triggers given using 6500 IU recombinant hCG plus 0.2 mg triptorelin. The primary outcome is number of mature (MII) oocytes retrieved, and secondary outcomes include fertilization rates, embryo counts, and implantation rates. Outcomes will be compared between the two groups using the clinic’s standard stimulation protocols and monitoring visits.
Why it matters
Potential benefit: If successful, this approach could increase the number of mature eggs retrieved in older poor-responder patients, potentially improving fertilization and embryo availability per cycle.
How similar studies have gone: While many studies compare trigger agents and timing, there is limited specific evidence on earlier triggering at 13–16 mm in older poor-responder (POSEIDON 4) patients, so this precise approach is relatively novel.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: * Women age equal to or greater than 35 years * Women with low serum AMH (\<1,2 ng/ml), * women with low AFC (\<5) * women Undergoing assisted reproduction with Short antagonist protocol or long -agonist protocol * women who used Max daily gonadotropin dose of 300 IU Exclusion Criteria: * Age \<35 years. * Ovarian reserve parameters not meeting the POSEIDON group 4 definition. * Natural or modified natural cycles without controlled ovarian stimulation. * In vitro maturation (IVM) cycles. * Luteal-phase stimulation or DuoStim protocols. * Preimplantation genetic testing (PGT-A, PGT-M, or PGT-SR) cycles, unless prespecified for stratified analyses. * Major untreated uterine cavity pathology (e.g., submucosal fibroids, significant intrauterine adhesions, congenital uterine anomalies) or untreated hydrosalpinx. * Cycles with missing or incomplete follicular measurement data on the trigger day. * Cycles with non-standardized or undocumented trigger-to-oocyte retrieval intervals.
Where it's running
-
Centrum Clinic IVF Center
Ankara, Ankara, Turkey (Türkiye) Recruiting
Study contacts
- Study coordinator: Emre G Pabuccu, Professor
- Email: emregpabuccu@gmail.com
- Phone: +90 532 4147844
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.