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NCT Number: NCT07818278

Cycle-to-cycle Variability of Progesterone in the Endometrium in Patients Undergoing an Euploid Blastocyst Transfer in a Hormone Replacement Therapy (HRT) Cycle (PROMICOFET)

This study looks at progesterone, a hormone that prepares the womb lining (endometrium) for pregnancy, in women having a frozen embryo transfer after IVF. Before an embryo is transferred, women take estrogen and progesterone medication to prepare the endometrium. Doctors currently check progesterone levels in the blood, but blood levels do not always match what is happening in the endometrium itself, and it is not yet known whether progesterone levels in the womb tissue stay the same from one treatment cycle to the next.

The study also looks at whether hormone levels relate to how the uterus contracts, to the bacteria naturally present in the vagina, cervix, uterus and gut, and to tiny particles released by cells (called extracellular vesicles) that may help the embryo and the womb "communicate" during implantation.

Participants are women who are already waiting for genetic test results on their embryos, a wait that typically lasts around 8 weeks. During this time, they go through two practice ("mock") treatment cycles using the same hormone medications as a real embryo transfer, but without an actual embryo. During these cycles, researchers collect blood and urine samples, a small tissue sample from the womb lining, swabs from the vagina, cervix and rectum, and a short ultrasound recording of womb movement. Afterwards, participants proceed with their real embryo transfer cycle, with similar (though fewer) measurements taken, and are followed to see whether they become pregnant.

The findings from this study may help doctors better understand how to personalize hormone treatment for future frozen embryo transfers, with the aim of improving pregnancy outcomes.

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Key information

Conditions

Fertility Implantation, Embryo

Age range

18 year–40 year

Sex eligibility

Female

Study type

Interventional

Phase

Phase 4

Primary location

About this study

This is a prospective, single-center pilot study conducted at the Department of Reproductive Medicine, Ghent University Hospital, in women undergoing preimplantation genetic testing for aneuploidy (PGT-A) prior to euploid blastocyst transfer in a hormone replacement therapy (HRT)-prepared frozen embryo transfer (FET) cycle. The pilot design was chosen because data on the interaction between endometrial and serum hormonal levels, the reproductive tract and fecal microbiome, uterine peristalsis, and embryo- and maternal-derived extracellular vesicles (EVs) in this setting are currently limited.

Each subject undergoes two mock HRT cycles during the approximately 8-week PGT-A waiting period, followed by one embryo transfer cycle. Endometrial preparation in each cycle consists of transdermal estradiol gel (Oestrogel®) until adequate endometrial thickness is reached, followed by vaginal micronized progesterone (Utrogestan®, 800 mg/day) for 6.5 days. In the mock cycles, no embryo is transferred; instead, study-specific procedures are performed, including endometrial biopsy for tissue hormonal quantification by UPLC-MS/MS, a mock embryo transfer with catheter tip collection for endometrial microbiome analysis, transvaginal ultrasound with speckle-tracking analysis of the uterine junctional zone to characterize contraction frequency, amplitude, and velocity before, during and after the procedure, and collection of vaginal, cervical and rectal swabs, urine, and blood for hormonal and extracellular vesicle profiling. The embryo transfer cycle follows the same sampling scheme (excluding endometrial biopsy) around an actual euploid blastocyst transfer performed under standard of care. Follicular fluid at oocyte pick-up and embryo culture media (collected on days 3 and 6 of embryo culture) are additionally retained for extracellular vesicle analysis, material that would otherwise be discarded during routine IVF laboratory processing.

Beyond the primary focus on intercycle reproducibility of endometrial tissue progesterone, the study explores associations between hormonal levels, uterine contractility, reproductive-tract and fecal microbiome composition, and extracellular vesicle cargo, with the broader aim of identifying candidate biomarkers of endometrial receptivity to inform future optimization of luteal phase support.

Given the established safety profile of the authorized study medications (Utrogestan® and Oestrogel®), adverse event and serious adverse event collection is selective, focused on events not attributable to standard-of-care fertility procedures; a Data Safety Monitoring Board was not deemed necessary.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥18 and ≤40 years old.
  • BMI ≥ 18 kg/m² and < 35 kg/m².
  • Current pregnancy wish.
  • PGT-A tested patients, undergoing a euploid blastocyst transfer in an artificial cycle.
  • Dutch, French and/or English speakers, as informed consent forms (ICFs) are made in those three languages.

Exclusion criteria

  • Known reasons for impaired implantation (specifically: presence of a hydrosalpinx; presence of a type I, II or III fibroid; Asherman's syndrome; uterine malformations; intrauterine adhesions; ≥ grade 3 endometriosis according to the ASRM classification, endometrial tuberculosis, adenomyosis).
  • Abnormal (not menstrual) vaginal bleeding without a known/diagnosed cause.
  • Tumours of the ovary, breast, uterus, pituitary or hypothalamus.
  • Untreated and uncontrolled thyroid dysfunction.
  • Personal history of a thromboembolic event.
  • Use of carbamazepine, rifampicin, phenytoin.
  • Subjects unable to comprehend the investigational nature of the proposed study.
  • Patients with a history of known thin endometrium (< 5 mm).

Treatment and study plan

Oestrogel® 0.75 mg (estradiol transdermal gel)

Drug

Oestradiol gel for endometrial preparation. Two pumps need to be administered in the morning (between 6 and 8 am) and two pumps in the evening (between 6 and 8 pm). In total, 3mg of estradiol per day.

Other names: estradiol, estradiol gel, transdermal oestradiol, oestrogel

Progesterone 200 mg vaginal capsules

Drug

Utrogestan®, 800 mg/day (in 200mg capsules) for 6.5 days

Other names: utrogestan, progesterone

endometrial biopsy

Procedure

Pipelle-based endometrial tissue sampling performed during each of the two mock HRT cycles (not during the actual transfer cycle), for determination of tissue progesterone, estradiol (and where sufficient tissue remains, estrone and 17-OHP) by UPLC-MS/MS, and for derivation of organoids/cells for in vitro assays.

Other names: endometrial sample, endometrial tissue, uterine lining biopsy

Mock embryo transfer

Procedure

Catheter placement performed identically to a real embryo transfer but without loading an embryo, conducted during each mock cycle. The catheter tip is collected (rather than discarded) for endometrial microbiome analysis.

Other names: fake embryo transfer, practice embryo transfer

Transvaginal ultrasound with uterine peristalsis assessment

Procedure

Standardized 4-minute transvaginal ultrasound recordings performed before, during and after the (mock) embryo transfer in each of the three cycles, using speckle-tracking analysis of the junctional zone to quantify uterine contraction frequency, amplitude, velocity, coordination and direction.

Other names: uterine waves, uterine peristalsis, vaginal ultrasound

Biological sample collection (blood, urine, vaginal/cervical/rectal swabs, follicular fluid, embryo culture media)

Procedure

Study-specific collection of: blood samples for hormonal profiling (estradiol, estrone, progesterone, 17α-hydroxyprogesterone) and extracellular vesicle (EV) analysis; urine samples for EV isolation; vaginal, cervical, and rectal swabs for microbiome analysis; follicular fluid collected at oocyte pick-up (otherwise discarded in routine care); and embryo culture media collected on days 3 and 6 of culture - all for EV composition and cargo analysis.

Other names: blood sample, blood, urine, urine sample, vaginal swab, cervical swab, fecal swab, follicular fluid, follicular fluid collection, embryo culture media, embryo culture media collection

Embryo transfer catheter tip collection for bacterial DNA analysis

Procedure

Collection of catheter tips following embryo transfer (study cycle) and, separately, from 30 routine clinical embryo transfers in non-enrolled patients, for protocol optimization of bacterial DNA extraction and endometrial microbiome analysis.

Other names: embryo transfer catheter tip collection, ET catheter collection

Questionnaires and pain assessment (VAS)

Other

Patient-completed questionnaires on dietary habits and lifestyle (to support microbiome data interpretation) and a Visual Analogue Scale (VAS) pain-scoring questionnaire completed at the time of each (mock) embryo transfer.

Other names: questionnaire, questions, vas score, pain assessment, vas scale, Visual Analogue Scale

Primary outcomes

  1. Endometrial hormonal concentrations

    Time frame: For an individual patient: mock embryo transfer cycles 1 and 2. Approximately 8 weeks. For the whole study: through the study completion, approximately 2 years since start of recruitment.

    Endometrial biopsies will be taken in mock embryo transfer cycles 1 and 2, on the day of mock transfer (day 6 after progesterone administration). This tissue will be sent to the clinical biology department in the hospital UZ Gent, to perform UPLC-MS/MS and obtain the concentration of progesterone, estradiol, estrone, 17α-hydroxyprogesterone in the tissue. This will later be correlated with the other outcome measurements: hormonal levels in blood, microbiome composition, uterine peristalsis, EV composition, etc. The concentrations will be obtained in ng/ml or μg/ml.

Secondary outcomes

  1. Hormonal levels in blood

    Time frame: From OPU (oocyte pick-up day) until pregnancy follow-up visit (between 6 and 8 weeks of gestation)

    Analysis of progesterone, oestradiol, oestrone and 17-alphahydroxyprogesterone concentration in blood and correlation with endometrial levels.

  2. Microbiome composition

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    Microbiome composition in the vagina, cervix, uterus and rectum; via swabs and embryo transfer catherter tip. The samples will be collected on the day of (mock) embryo transfer through the three identically prepared HRT cycles.

  3. Clinical pregnancy outcomes: biochemical pregnancy

    Time frame: Follow-up pregnancy visit (6-8 weeks of gestation)

    Clinical pregnancy outcomes will be measured with percentage of patients that reach:

    • Biochemical pregnancy: if no gestational sac was seen in the ultrasound during the follow-up pregnancy visit (6-8 weeks of gestation), but there is a positive blood or urine test measuring human chorionic gonadotropin (hCG).

  4. Clinical pregnancy outcomes: live birth

    Time frame: Follow-up pregnancy (6-8 weeks of gestation) until live birth (up to approximately 40 weeks after embryo transfer)

    Clinical pregnancy outcomes will be measured with percentage of patients that reach:

    • Live Birth Rate: The delivery of a live infant after 24 to 28 weeks of gestation, considered the gold-standard endpoint in fertility trials.

  5. Clinical pregnancy outcome: miscarriage

    Time frame: From the follow-up pregnancy (6-8 weeks of gestation) visit until miscarriage happens (before 22 completed weeks of gestational age).

    Clinical pregnancy outcomes will be measured with percentage of patients that reach:

    • Miscarriage Rate: The spontaneous loss of a verified clinical pregnancy before 22 completed weeks of gestational age

  6. Clinical pregnancy outcome: clinical pregnancy

    Time frame: Follow-up pregnancy visit (6-8 weeks of gestation)

    Clinical pregnancy outcomes will be measured with percentage of patients that reach:

    • Clinical Pregnancy: Confirmed by ultrasound at 6-8 weeks showing a heartbeat or gestational sac, distinguishing it from a purely chemical (biochemical) pregnancy detected only by blood or urine hormone tests.

  7. Questionnaire about lifestyle and dietary habits for better analysis of microbiome composition

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    This questionnaire mostly has questions that can be answered with YES/NO, being the remaining questions a multiple choice questions, or a fill in question (mostly if they check "yes" and we need more information, for example if they said they used antibiotics in the last 30 days, to ask which product, dose and duration of the treatment, and until when). The data will be expressed as percentage of patients answering "yes", or percentage of patients selecting each option (in multiple choice questions).

  8. Visual Analogue Scale (VAS) for (mock) embryo transfer

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    Visual Analogue Scale (VAS) for pain assessment during (mock) embryo transfer procedures. The VAS score goes from 0 to 10, being 0 no pain, and being 10 the worst pain.

  9. Uterine waves/peristalsis analysis - contraction coordination

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    One of the uterine waves parameters we will obtain is the contraction coordination, which represents if anterior and posterior walls move synchronously or asynchronously to each other. A higher value shows decreased coordination. It does not have units but it is expressed in mean squared error. This will be assessed before, during and after embryo transfer by 4-minute TVUS video recording.

  10. Uterine waves/peristalsis analysis - contraction velocity

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    One of the uterine waves parameters we will obtain is the contraction velocity, which analyses at which speed do the waves propagate in a certain direction (F2C or C2F). This is obtained by first analysing the radial strain signal in the spatiotemporal frequency domain (20 seconds) and then averaging the velocities over time in the corresponding direction (C2F or F2C). A high value represents increased velocity in that direction. It is expressed in mm/s.

    This will be assessed before, during and after embryo transfer by 4-minute TVUS video recording.

  11. Uterine waves/peristalsis analysis - contraction direction

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    One of the uterine waves parameters we will obtain is the contraction direction, which explains whether the wave propagates fondus to cervix (F2C) or cervix to fondus (C2F). It has no units. Positive value is F2C, negative value is C2F and a value of 0 is a movement without predominant direction (opposing contractions). This will be assessed before, during and after embryo transfer by 4-minute TVUS video recording.

  12. Uterine waves/peristalsis analysis - contraction amplitude

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    One of the uterine waves parameters we will obtain is the contraction amplitude, which reflects the strength of uterine contraction. It is obtained by calculating SD of the strain signal in the longitudinal and radial directions from its frequency spectrum. It has no units. This will be assessed before, during and after embryo transfer by 4-minute TVUS video recording.

  13. Uterine waves/peristalsis analysis - contraction frequency

    Time frame: On the day of (mock) embryo transfer through the three identically prepared HRT cycles. Approximately 3 months per patient.

    One of the uterine waves parameters we will obtain is the contraction frequency, which is the amount of contractions per minute (unit of measurement contractions/minute). This will be assessed before, during and after embryo transfer by 4-minute TVUS video recording.

  14. EVs composition in blood, follicular fluid and urine (maternal), and embryo culture media

    Time frame: From OPU (oocyte pick-up day) until pregnancy follow-up (between 6 and 8 weeks of gestation)

    EVs cargo and composition analysis and RNA sequencing

Study contacts

Contact information is provided by the study sponsor or research team.

Dominic Stoop, Prof. dr.

CONTACT

[email protected]

93321699 ext. +32

Paula Iglesias Moreno, MSc

CONTACT

[email protected]

93325631 ext. +32

Sponsors and collaborators

Lead sponsor

University Hospital, Ghent

Other

Collaborators

  • Besins Healthcare

Registry information

Acronym: PROMICOFET

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Sep 14, 2026
Registry last updated
Sep 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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