FertilizationBESTNCT06433518
BEst Size for Ovulation Triggering in Poseidon 4 Patients (BEST 4 Study)
An observational study of Fertilization and Fertilization in Vitro, run by Centrum Clinic IVF Center at 1 site in Turkey (Türkiye).
Trial summary
This observational clinical study aims to determine the optimal timing of ovulation triggering in women aged 35 and above with poor ovarian reserve. For this purpose, cases undergoing ovarian stimulation for assisted reproductive treatment and planned final oocyte triggering will be evaluated in two separate groups… Read more about this study
- Who is it for?
- Ages 35 to 44 years, women only
- Conditions the study is for
- Fertilization, Fertilization in Vitro
- What is being tested?
- Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF Patients
- How many people
- 200 participants
- Where
- 1 siteTurkey (Türkiye)
- Study dates
- 15 Mar 2026to 30 Dec 2026
- How long will I take part?
- 9 Months
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 35 to 44 years
- Women only
- No healthy volunteers
- Adult
Study population: A group of women defined as Poseidon Group 4, who will apply to the infertility clinic to be scheduled for ovarian stimulation and assisted conception treatments during the study period.
Who may be able to join
- 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
Who cannot join
- 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.
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- 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.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Turkey (Türkiye)1 site, 1 recruiting
- Recruiting
Centrum Clinic IVF Center
Ankara, Ankara, 06800
Emre Pabuccu, 05324147844
About this study
Official title: What Should Be The Optimal Ovulation Triggering Size in Poseidon Group 4 Patients Undergoing Ovarian Stimulation?
This observational clinical study aims to determine the optimal timing of ovulation triggering in women aged 35 and above with poor ovarian reserve.
For this purpose, cases undergoing ovarian stimulation for assisted reproductive treatment and planned final oocyte triggering will be evaluated in two separate groups:
Read more
- Experimental Group: Final oocyte triggering will be performed when the follicle or follicles measure between 13-16 mm.
- Control Group: Final oocyte triggering will be performed when the follicle or follicles measure greater than 17 mm.
All triggers will be administered uniformly with 6500 units of recombinant hCG and 0,2 mg triptorelin injections.
The primary outcome of the study will be the number of mature oocytes. Secondary outcomes will include fertilization rates, embryo counts, and implantation rates.
Primary and secondary outcomes will be compared between the two groups.
Read the detailed description
The timing of final oocyte maturation in assisted reproductive techniques is critically important. If serum steroid hormone levels are appropriate during the late follicular phase, ovulation triggering can be performed using various agents. There are numerous comparative studies in the literature on this topic.
However, a key issue is determining the most optimal timing for this trigger. In standard practice, the final triggering is performed when the follicle size reaches 17 mm or more.
The purpose of this is to obtain mature eggs from these follicles during the oocyte aspiration process.
However, in some special cases, to maximize the desired yield, this size threshold may be adjusted.
A prime example of this is in older patients with poor ovarian reserve, as the expected egg yield may not be achieved with standard practices.
During the oocyte collection process, fewer mature oocytes (M2) may be retrieved, or no oocytes may be retrieved at all, despite proper ovarian stimulation. Therefore, the optimal follicle size for these cases has not been definitively established in the literature. Thus, there is a need to determine other follicular thresholds specifically for older women with poor ovarian reserves to enhance egg and mature egg yields.
For this purpose, cases undergoing ovarian stimulation for assisted reproductive treatment and planned final oocyte triggering will be evaluated in two separate groups:
- Experimental Group: Final oocyte triggering will be performed when the follicle or follicles measure between 13-16 mm.
- Control Group: Final oocyte triggering will be performed when the follicle or follicles measure greater than 17 mm.
All triggers will be administered uniformly with 6500 units of recombinant hCG and 0,2 mg triptorelin injections.
The primary outcome of the study will be the number of mature oocytes. Secondary outcomes will include fertilization rates, embryo counts, and implantation rates.
Primary and secondary outcomes will be compared between the two groups.
- Conditions
- Fertilization, Fertilization in Vitro
- Being tested
- Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF Patients
- Keywords
- oocyte, IVF, poor responder, ovarian stimulation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF PatientsOther
In this study, ovulation trigger timing is determined according to the diameter of the leading follicle measured by transvaginal ultrasound during ovarian stimulation in women classified as POSEIDON group 4. Patients undergoing controlled ovarian stimulation are monitored with serial ultrasound examinations and serum hormone measurements. Ovulation triggering is performed when the leading follicle reaches predefined size categories. The study evaluates the association between the diameter of the leading follicle at the time of trigger and reproductive outcomes. The primary outcome measure is the number of metaphase II (MII) oocytes retrieved, while secondary outcomes include blastocyst formation and pregnancy outcomes.
| Study group | Role | What they receive |
|---|---|---|
| Women defined as poor responders according to POSEIDON criteria group 4 undergoing IVF | This group of women, who have low serum AMH levels and low antral follicle count obviusly reveal unfavorable ovarian stimulation and reproductive outcomes in daily practice. Since the most important outcome measure is the live birth rate in assisted reproduction, rates have been reportedly very low for this cohort. Depending from the reports, live birth rates particularly cumulative rates directly correlated with collected numbers of oocytes. Therefore, studies should focus on this entity. Receives: Other: Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF Patients |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in the Mean Mature Oocytes between two triggering strategies
Mean numbers of oocytes, mature oocytes, fertilization rates, embryos and pregnancy rates will be compared between two different triggering sizes.
Measured: From enrollment to the end of treatment at 6-8 months.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 May 2024
- Study start15 Mar 2026
- Primary completion1 Dec 2026 (estimated)
- Study completion30 Dec 2026 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for FertilizationStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Cohort
- Time perspective
- Prospective
- Enrolment
- 200 participants (estimated)
- Target duration
- 9 Months
Sponsor and investigators
- Lead sponsor
- Centrum Clinic IVF Center
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Emre Göksan Pabuçcu, Centrum Clinic IVF Center
- Investigators
- Emre Pabuccu, Prof., Study director, Ufuk University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06433518
- Sponsor's protocol ID
- 2024-3-1
- Acronym
- BEST
- Status last verified
- Feb 2026
- First submitted
- 23 May 2024
- Last updated
- 19 Mar 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 19 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- What Should Be The Optimal Ovulation Triggering Size in Poseidon Group 4 Patients Undergoing Ovarian Stimulation?
- ClinicalTrials.gov ID
- NCT06433518
- Acronym / sponsor ID
- BEST / 2024-3-1
- Conditions
- Fertilization, Fertilization in Vitro
- Keywords
- oocyte, IVF, poor responder, ovarian stimulation
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 200 participants (estimated)
- Lead sponsor
- Centrum Clinic IVF CenterUniversity, hospital or other
- Study start
- 15 Mar 2026 (actual)
- Primary completion
- 1 Dec 2026 (estimated)
- Study completion
- 30 Dec 2026 (estimated)
- First posted
- 29 May 2024 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This observational clinical study aims to determine the optimal timing of ovulation triggering in women aged 35 and above with poor ovarian reserve.
For this purpose, cases undergoing ovarian stimulation for assisted reproductive treatment and planned final oocyte triggering will be evaluated in two separate groups:
- Experimental Group: Final oocyte triggering will be performed when the follicle or follicles measure between 13-16 mm.
- Control Group: Final oocyte triggering will be performed when the follicle or follicles measure greater than 17 mm.
All triggers will be administered uniformly with 6500 units of recombinant hCG and 0,2 mg triptorelin injections.
The primary outcome of the study will be the number of mature oocytes. Secondary outcomes will include fertilization rates, embryo counts, and implantation rates.
Primary and secondary outcomes will be compared between the two groups.
Detailed description
The timing of final oocyte maturation in assisted reproductive techniques is critically important. If serum steroid hormone levels are appropriate during the late follicular phase, ovulation triggering can be performed using various agents. There are numerous comparative studies in the literature on this topic.
However, a key issue is determining the most optimal timing for this trigger. In standard practice, the final triggering is performed when the follicle size reaches 17 mm or more.
The purpose of this is to obtain mature eggs from these follicles during the oocyte aspiration process.
However, in some special cases, to maximize the desired yield, this size threshold may be adjusted.
A prime example of this is in older patients with poor ovarian reserve, as the expected egg yield may not be achieved with standard practices.
During the oocyte collection process, fewer mature oocytes (M2) may be retrieved, or no oocytes may be retrieved at all, despite proper ovarian stimulation. Therefore, the optimal follicle size for these cases has not been definitively established in the literature. Thus, there is a need to determine other follicular thresholds specifically for older women with poor ovarian reserves to enhance egg and mature egg yields.
For this purpose, cases undergoing ovarian stimulation for assisted reproductive treatment and planned final oocyte triggering will be evaluated in two separate groups:
- Experimental Group: Final oocyte triggering will be performed when the follicle or follicles measure between 13-16 mm.
- Control Group: Final oocyte triggering will be performed when the follicle or follicles measure greater than 17 mm.
All triggers will be administered uniformly with 6500 units of recombinant hCG and 0,2 mg triptorelin injections.
The primary outcome of the study will be the number of mature oocytes. Secondary outcomes will include fertilization rates, embryo counts, and implantation rates.
Primary and secondary outcomes will be compared between the two groups.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Target follow-up
- 9 Months
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Women defined as poor responders according to POSEIDON criteria group 4 undergoing IVF | – | Other: Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF PatientsThis group of women, who have low serum AMH levels and low antral follicle count obviusly reveal unfavorable ovarian stimulation and reproductive outcomes in daily practice. Since the most important outcome measure is the live birth rate in assisted reproduction, rates have been reportedly very low for this cohort. Depending from the reports, live birth rates particularly cumulative rates directly correlated with collected numbers of oocytes. Therefore, studies should focus on this entity. |
Who may qualify
- Ages
- 35 to 44 years
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult
- Study population
- A group of women defined as Poseidon Group 4, who will apply to the infertility clinic to be scheduled for ovarian stimulation and assisted conception treatments during the study period.
Key inclusion criteria (5 listed)
- 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
Key exclusion criteria (9 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Ovulation Trigger Timing Based on Leading Follicle Size in POSEIDON Group 4 IVF PatientsIn this study, ovulation trigger timing is determined according to the diameter of the leading follicle measured by transvaginal ultrasound during ovarian stimulation in women classified as POSEIDON group 4. Patients undergoing controlled ovarian stimulation are monitored with serial ultrasound examinations and serum hormone measurements. Ovulation triggering is performed when the leading follicle reaches predefined size categories. The study evaluates the association between the diameter of the leading follicle at the time of trigger and reproductive outcomes. The primary outcome measure is the number of metaphase II (MII) oocytes retrieved, while secondary outcomes include blastocyst formation and pregnancy outcomes. | Other | Women defined as poor responders according to POSEIDON criteria group 4 undergoing IVF |
Primary outcome
Change in the Mean Mature Oocytes between two triggering strategies
Time frame: From enrollment to the end of treatment at 6-8 months.
Mean numbers of oocytes, mature oocytes, fertilization rates, embryos and pregnancy rates will be compared between two different triggering sizes.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 19 Mar 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Emre Pabuccu, Prof. study director
Ufuk University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Fertilization and Fertilization in Vitro, run by Centrum Clinic IVF Center at 1 site in Turkey (Türkiye).
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 5 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 19 Mar 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Emre G Pabuccu, Professor (+90 532 4147844, emregpabuccu@gmail.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in the Mean Mature Oocytes between two triggering strategies (time frame: From enrollment to the end of treatment at 6-8 months.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 19 Mar 2026.