Evaluating the convenience of natural cycle frozen embryo transfer

Assessing the Convenience of Natural Proliferative Phase Frozen Embryo Transfer: an Ambispective Cohort Study

Observational Instituto Valenciano de Infertilidade de Lisboa · NCT06307184

This study looks at whether a new method for frozen embryo transfer that uses the body's natural cycle is easier and more convenient for patients compared to the traditional method that relies on medication.

Quick facts

Study typeObservational
Enrollment530 (estimated)
Ages18 Years to 49 Years
SexFemale
SponsorInstituto Valenciano de Infertilidade de Lisboa Research network
Locations1 site (Lisbon)
Trial IDNCT06307184 on ClinicalTrials.gov

What this trial studies

This observational study aims to assess the convenience of the natural proliferative phase frozen embryo transfer (NPP-FET) protocol by analyzing the number of appointments required before scheduling the transfer. The study compares NPP-FET with traditional artificial cycle frozen embryo transfer (AC-FET), which is often preferred for its scheduling ease despite potential risks associated with it. The research focuses on patients undergoing frozen embryo transfer in assisted reproductive technology (ART) clinics, particularly those using donated oocytes. By examining the convenience and outcomes of NPP-FET, the study seeks to provide insights into optimizing embryo transfer protocols.

Who should consider this trial

Good fit: Ideal candidates for this study are women with regular menstrual cycles who are undergoing their first or second frozen embryo transfer using a single blastocyst from donated oocytes.

Not a fit: Patients who have a history of recurrent pregnancy loss or implantation failure, or those requiring exogenous ovarian stimulation during the transfer, may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could lead to a more convenient and effective approach for patients undergoing frozen embryo transfers, potentially improving pregnancy outcomes.

How similar studies have performed: While there is growing evidence supporting the use of natural cycle protocols, this specific approach of NPP-FET is relatively novel and has not been extensively tested in prior studies.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Endometrial thickness ≥ 7 mm on the day of starting progesterone-based luteal phase support (LPS)
* Serum progesterone levels \<1.5 ng/ml on the day of starting progesterone-based LPS
* LPS with micronized progesterone 400mg b.i.d.
* Regular cycles (\>24 days, ≤ 38 days)
* IVF/ICSI with donated oocytes
* Single blastocyst stage embryo transfer
* First or second embryo transfer from the same cohort

Exclusion Criteria:

* Use of exogenous ovarian stimulation during FET
* Untreated hydrosalpinx, polyp, submucous myomas or severe adenomyosis
* Recurrent pregnancy loss (≥ 3 previous pregnancy losses)
* Recurrent implantation failure with embryos from oocyte donation (≥ 3 previous failed embryo transfers)
* Personalized initiation of exogenous progesterone according to a previous endometrial receptivity assay test

Where this trial is running

Lisbon

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Frozen Embryo TransferEndometrial preparationNatural cycleProgesteronePregnancy
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.