Menstrual CycleCLEARNCT07648381
Corpus Luteum Function and Cardiovascular Adaptation in a Natural MOCK Cycle.
An observational study of Menstrual Cycle and Luteal Phase Progesterone Levels, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
Trial summary
In infertility treatment, embryos are created in vitro after eggs have been fertilised by sperm using in vitro fertilisation or intracytoplasmic sperm injection techniques. These embryos, resulting from hormonal ovarian stimulation, can be transferred shortly after egg retrieval (fresh transfer) or frozen for later… Read more about this study
- Who is it for?
- Ages 18 to 40 years, women onlyHealthy volunteers can take part
- Conditions the study is for
- Menstrual Cycle, Luteal Phase Progesterone Levels, Luteal Phase Adaptation
- What is being tested?
- Blood samples for the analysis of biomarkers., Transvaginal ultrasound for follicle and endometrium measurements. and Mean Arterial Pressure measurement.
- Type of treatment
- Injection or infusion
- How many people
- 118 participants
- Where
- 1 siteBelgium
- Study dates
- 1 Jul 2026to Sep 2028
- 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 18 to 40 years
- Women only
- Healthy volunteers accepted
- Adult
Study population: Our study population pertains to female patients and volunteers, of the age between 18 years old and 40 years old, with a regular menstrual cycle (25-35 days) and a normal BMI (18.5-35). You are eligible if you have not used any form of hormonal contraception or copper IUD throughout the last 3 months, have not had an ovarian stimulation during this time period, and are not known with renal or cardiac disease, diabetes or hypertension.
Who may be able to join
- Age below 40 years
- Regular menstrual cycles (between 25-35 days)
- Normal BMI between 18.5 and 35
Who cannot join
- Underlying renal or cardiac disease
- Hypertension
- Diabetes mellitus
- Contraceptive use less than 3 months before MOCK cycle, including: IUD (hormonal and copper), hormonal patch, contraceptive pill (combination and mini), hormonal intravaginal ring, contraceptive implant, contraceptive injection.
- Ovarian stimulation during the previous three months
- History of recurrent pregnancy loss (defined as 2 or more previous pregnancy losses before 24 weeks gestation).
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Belgium1 site
UZ Brussel
Jette, 1090
Caroline Roelens, 0032 2 477 9887, caroline.roelens@uzbrussel.be
About this study
In infertility treatment, embryos are created in vitro after eggs have been fertilised by sperm using in vitro fertilisation or intracytoplasmic sperm injection techniques. These embryos, resulting from hormonal ovarian stimulation, can be transferred shortly after egg retrieval (fresh transfer) or frozen for later use. Both natural menstrual cycles and artificial cycles (using hormones to mimic a normal cycle) can prepare the uterus for embryo transfer. Patients with regular menstrual cycles often prefer the non-medicated approach. However, these cycles offer less flexibility in timing because they rely on ovulation. As the number of FET cycles increases worldwide, scientists are exploring the possibility of inducing ovulation in smaller follicles to increase the flexibility of natural cycles. However, the safety for future pregnancies is unknown. This study aims to better understand the function of the corpus luteum, the follicle remnant in the ovary after ovulation, by measuring several factors that change throughout the cycle due to substances produced by the corpus luteum. The results of the study will have a direct impact on clinical practice by increasing the flexibility of frozen transfer cycles.
- Being tested
- Blood samples for the analysis of biomarkers., Transvaginal ultrasound for follicle and endometrium measurements., Mean Arterial Pressure measurement., Ovitrelle injection for ovulation induction
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Blood samples for the analysis of biomarkers.Diagnostic test
We will collect several blood samples:
- One at day 8 of the cycle: measurements of P, E2, Na, K, CL, CO2, Osmolality, PRL, direct renin, PAC, Nt-proBNP, Relaxin-2 and VEGF.
- One for cycle follow up between day 8 and ovulation: measurement of P, E2, LH
- One at day 7 after ovulation induction: measurements of P, E2, Na, K, CL, CO2, Osmolality, PRL, direct renin, PAC, Nt-proBNP, Relaxin-2 and VEGF.
Transvaginal ultrasound for follicle and endometrium measurements.Diagnostic test
A transvaginal ultrasound will be performed after day 8 of the cycle to evaluate a 2D measurement of the growing follicle, as well as a measurement of the endometrial thickness to evaluate readiness for ovulation induction.
Mean Arterial Pressure measurement.Diagnostic test
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Ovitrelle injection for ovulation inductionDrug
When patient is deemed ready for ovulation based on follicle size, blood results and endometrium, she will be asked to inject Ovitrelle 250 micrograms to induce ovulation in a controlled and timed manner.
| Study group | Role | What they receive |
|---|---|---|
| Follicle size 11mm | Patients with a follicle of 11mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 12 mm | Patients with a follicle of 12mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 13 mm | Patients with a follicle of 13mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 14 mm | Patients with a follicle of 14mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 15 mm | Patients with a follicle of 15mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 16 mm | Patients with a follicle of 16mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 17 mm | Patients with a follicle of 17mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction | |
| Follicle size 18 mm | Patients with a follicle of 18mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. Receives: Diagnostic Test: Blood samples for the analysis of biomarkers.; Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements.; Diagnostic Test: Mean Arterial Pressure measurement.; Drug: Ovitrelle injection for ovulation induction |
What is being measured
The primary outcome is the main question the study is designed to answer.
The relationship between progesterone levels and different follicular sizes on day 7 post ovulation induction.
Progesterone levels will be measured 7 days after ovulation induction to relate them to different follicular sizes.
Measured: From the start of the menstrual cycle until 7 days after ovulation induction.
Secondary outcomes (2)
Estradiol evolution throughout the cycle and its relation to luteal progesterone levels.
We will measure the estradiol on different moments throught the menstural cycle, and see how these levels correspond to later (luteal) progesterone levels.
Measured: From the start of a menstrual cycle until 7 days post-ovulation induction.
Indirect factors reflecting cardiovascular and renal adaptation in the luteal phase
We will measure these factors (MAP, progesterone, estradiol, serum sodium, chloride, carbon dioxide and osmolality, prolactin, direct renin, plasma aldosterone, NT-proBNP, relaxin-2 and VEGF) at day 8 of the cycle, as well as 7 days after ovulation-induction. All these factors form a reflection of the body's cardiovascular and renal adaptation, and will be studied to estimate these adaptation at different follicular sizes.
Measured: From the start of the menstrual cycle until 7 days after ovulation induction.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted15 Jun 2026
- Study start1 Jul 2026 (estimated)
- Primary completionFeb 2028 (estimated)
- Study completionSep 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Menstrual CycleStudies of the same condition, open and under way.
- More trials run by Universitair Ziekenhuis BrusselThe sponsor's other registered studies.
- 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
- 118 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Universitair Ziekenhuis Brussel
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Noa Wauters, Universitair Ziekenhuis Brussel
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07648381
- Sponsor's protocol ID
- EC-2025-445
- Acronym
- CLEAR
- Status last verified
- Jun 2026
- First submitted
- 9 Jun 2026
- Last updated
- 15 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 15 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Corpus Luteum Function and Cardiovascular Adaptation in a Natural MOCK Cycle.
- ClinicalTrials.gov ID
- NCT07648381
- Acronym / sponsor ID
- CLEAR / EC-2025-445
- Study type
- Observational
- Recruitment status
- Not yet recruiting
- Enrolment
- 118 participants (estimated)
- Lead sponsor
- Universitair Ziekenhuis BrusselUniversity, hospital or other
- Study start
- 1 Jul 2026 (estimated)
- Primary completion
- Feb 2028 (estimated)
- Study completion
- Sep 2028 (estimated)
- First posted
- 15 Jun 2026 (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.
In infertility treatment, embryos are created in vitro after eggs have been fertilised by sperm using in vitro fertilisation or intracytoplasmic sperm injection techniques. These embryos, resulting from hormonal ovarian stimulation, can be transferred shortly after egg retrieval (fresh transfer) or frozen for later use. Both natural menstrual cycles and artificial cycles (using hormones to mimic a normal cycle) can prepare the uterus for embryo transfer. Patients with regular menstrual cycles often prefer the non-medicated approach. However, these cycles offer less flexibility in timing because they rely on ovulation. As the number of FET cycles increases worldwide, scientists are exploring the possibility of inducing ovulation in smaller follicles to increase the flexibility of natural cycles. However, the safety for future pregnancies is unknown. This study aims to better understand the function of the corpus luteum, the follicle remnant in the ovary after ovulation, by measuring several factors that change throughout the cycle due to substances produced by the corpus luteum. The results of the study will have a direct impact on clinical practice by increasing the flexibility of frozen transfer cycles.
Study design
- Observational model
- Cohort
- Time perspective
- Prospective
- Number of arms
- 8
| Arm | Type | Receives |
|---|---|---|
| Follicle size 11mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 11mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 12 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 12mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 13 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 13mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 14 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 14mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 15 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 15mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 16 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 16mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 17 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 17mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
| Follicle size 18 mm | – | Diagnostic Test: Blood samples for the analysis of biomarkers., Diagnostic Test: Transvaginal ultrasound for follicle and endometrium measurements., Diagnostic Test: Mean Arterial Pressure measurement., Drug: Ovitrelle injection for ovulation inductionPatients with a follicle of 18mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction. |
Who may qualify
- Ages
- 18 to 40 years
- Sex
- Female only
- Healthy volunteers
- Accepted
- Age groups
- Adult
- Study population
- Our study population pertains to female patients and volunteers, of the age between 18 years old and 40 years old, with a regular menstrual cycle (25-35 days) and a normal BMI (18.5-35). You are eligible if you have not used any form of hormonal contraception or copper IUD throughout the last 3 months, have not had an ovarian stimulation during this time period, and are not known with renal or cardiac disease, diabetes or hypertension.
Key inclusion criteria (3 listed)
- Age below 40 years
- Regular menstrual cycles (between 25-35 days)
- Normal BMI between 18.5 and 35
Key exclusion criteria (6 listed)
- Underlying renal or cardiac disease
- Hypertension
- Diabetes mellitus
- Contraceptive use less than 3 months before MOCK cycle, including: IUD (hormonal and copper), hormonal patch, contraceptive pill (combination and mini), hormonal intravaginal ring, contraceptive implant, contraceptive injection.
- Ovarian stimulation during the previous three months
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 |
|---|---|---|
| Blood samples for the analysis of biomarkers.We will collect several blood samples: * One at day 8 of the cycle: measurements of P, E2, Na, K, CL, CO2, Osmolality, PRL, direct renin, PAC, Nt-proBNP, Relaxin-2 and VEGF. * One for cycle follow up between day 8 and ovulation: measurement of P, E2, LH * One at day 7 after ovulation induction: measurements of P, E2, Na, K, CL, CO2, Osmolality, PRL, direct renin, PAC, Nt-proBNP, Relaxin-2 and VEGF. | Diagnostic test | Follicle size 11mm, Follicle size 12 mm, Follicle size 13 mm, Follicle size 14 mm, Follicle size 15 mm, Follicle size 16 mm, Follicle size 17 mm, Follicle size 18 mm |
| Transvaginal ultrasound for follicle and endometrium measurements.A transvaginal ultrasound will be performed after day 8 of the cycle to evaluate a 2D measurement of the growing follicle, as well as a measurement of the endometrial thickness to evaluate readiness for ovulation induction. | Diagnostic test | Follicle size 11mm, Follicle size 12 mm, Follicle size 13 mm, Follicle size 14 mm, Follicle size 15 mm, Follicle size 16 mm, Follicle size 17 mm, Follicle size 18 mm |
| Mean Arterial Pressure measurement.The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations. | Diagnostic test | Follicle size 11mm, Follicle size 12 mm, Follicle size 13 mm, Follicle size 14 mm, Follicle size 15 mm, Follicle size 16 mm, Follicle size 17 mm, Follicle size 18 mm |
| Ovitrelle injection for ovulation inductionWhen patient is deemed ready for ovulation based on follicle size, blood results and endometrium, she will be asked to inject Ovitrelle 250 micrograms to induce ovulation in a controlled and timed manner. | Drug | Follicle size 11mm, Follicle size 12 mm, Follicle size 13 mm, Follicle size 14 mm, Follicle size 15 mm, Follicle size 16 mm, Follicle size 17 mm, Follicle size 18 mm |
Primary outcome
The relationship between progesterone levels and different follicular sizes on day 7 post ovulation induction.
Time frame: From the start of the menstrual cycle until 7 days after ovulation induction.
Progesterone levels will be measured 7 days after ovulation induction to relate them to different follicular sizes.
2 secondary outcomes
Estradiol evolution throughout the cycle and its relation to luteal progesterone levels.
Time frame: From the start of a menstrual cycle until 7 days post-ovulation induction.
Indirect factors reflecting cardiovascular and renal adaptation in the luteal phase
Time frame: From the start of the menstrual cycle until 7 days after ovulation induction.
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 15 Jun 2026.
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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.
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 Menstrual Cycle and Luteal Phase Progesterone Levels, run by Universitair Ziekenhuis Brussel at 1 site in Belgium.
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 3 inclusion and 6 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: opening soon, as of the sponsor's last update on 15 Jun 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 Belgium. 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 Caroline Roelens (0032 2 477 9887, caroline.roelens@uzbrussel.be), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
The relationship between progesterone levels and different follicular sizes on day 7 post ovulation induction. (time frame: From the start of the menstrual cycle until 7 days after ovulation induction.). 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 15 Jun 2026.