Comparing Day 6 and Day 7 Blastocyst Transfers in Frozen HRT Cycles

Optimal Timing of Euploid Day 6 Blastocyst (blastocyst Which Was Biopsied on Day 6 After Fertilization) Transfer in Frozen Hormonal Replacement Therapy Cycles: Day 6 or Day 7 of Progesterone Administration?

PHASE1 · ART Fertility Clinics LLC · NCT05980091

This study is testing whether transferring frozen embryos on day 6 or day 7 of hormone treatment can lead to better pregnancy outcomes for women using frozen embryo transfers.

Quick facts

PhasePHASE1
Study typeInterventional
Enrollment316 (estimated)
Ages18 Years to 43 Years
SexFemale
SponsorART Fertility Clinics LLC (other)
Locations2 sites (Abu Dhabi, Abu Dhabi Emirate and 1 other locations)
Trial IDNCT05980091 on ClinicalTrials.gov

What this trial studies

This study aims to evaluate the clinical pregnancy, miscarriage, and live birth rates associated with transferring euploid day 6 blastocysts on either the 6th or 7th day of progesterone administration in Hormonal Replacement Therapy (HRT) frozen embryo transfer cycles. It is a prospective and randomized trial that will focus exclusively on euploid embryos to eliminate aneuploidy as a factor in implantation failure. The research seeks to determine the optimal timing for embryo transfer to enhance pregnancy outcomes by ensuring synchronization between the embryo and the endometrial window of implantation.

Who should consider this trial

Good fit: Ideal candidates include women aged 18 to 43 with at least one euploid cryopreserved day 6 blastocyst of Grade BB quality.

Not a fit: Patients with uterine abnormalities, hydrosalpinx, or any contraindications to estradiol or progesterone may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could improve pregnancy rates for women undergoing frozen embryo transfers.

How similar studies have performed: This approach is novel, as it is the first prospective study specifically examining euploid day 6 blastocyst transfers.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Women aged 18 years to 43 years.
* Having at least 1 euploid cryopreserved day 6 blastocyst of at least Grade BB quality.
* Endometrial trilaminar appearance on the day of progesterone start

Exclusion Criteria:

* Uterine abnormality
* Hydrosalpinx
* Asherman syndrome
* Any known contraindications or allergy to oral estradiol or progesterone.
* Intention to treat : exclusion factors :

  1. Spontaneous ovulation HRT cycle
  2. Discontinuation of HRT medication

Where this trial is running

Abu Dhabi, Abu Dhabi Emirate and 1 other locations

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.

View on ClinicalTrials.gov →

Conditions: Infertility, Fertility Issues, Infertility, Female, Implantation, Blastocyst, HRT, Progesterone

Last reviewed 2026-05-15 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.