Corpus Luteum Function and Cardiovascular Adaptation in a Natural MOCK Cycle. (CLEAR)

June 9, 2026 updated by: Noa Wauters, Universitair Ziekenhuis Brussel
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 Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
118

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Probability Sample

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.

Description

Inclusion Criteria:

  • Age below 40 years
  • Regular menstrual cycles (between 25-35 days)
  • Normal BMI between 18.5 and 35

Exclusion Criteria:

  • 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).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Follicle size 11mm
Patients with a follicle of 11mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 12 mm
Patients with a follicle of 12mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 13 mm
Patients with a follicle of 13mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 14 mm
Patients with a follicle of 14mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 15 mm
Patients with a follicle of 15mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 16 mm
Patients with a follicle of 16mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 17 mm
Patients with a follicle of 17mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.
Follicle size 18 mm
Patients with a follicle of 18mm when measured through transvaginal ultrasound in 2D, at time of ovulation induction.
Diagnostic test: 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: 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: Mean Arterial Pressure measurement.
The MAP will be measured at cycle day 7 and 7 days post-ovulation induction to follow cardiovascular adaptations.
Drug: Ovitrelle injection for ovulation induction
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.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
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.
From the start of the menstrual cycle until 7 days after ovulation induction.

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
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.
We will measure the estradiol on different moments throught the menstural cycle, and see how these levels correspond to later (luteal) progesterone levels.
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.
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.
From the start of the menstrual cycle until 7 days after ovulation induction.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Universitair Ziekenhuis Brussel

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
July 1, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
February 1, 2028

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 1, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
June 9, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 9, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
June 15, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
June 15, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
June 9, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
June 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • EC-2025-445

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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