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Not yet recruiting NCT07425990

FET-LET-2x2: Clinical Pregnancy Rates After Frozen Embryo Transfer in Natural and Modified Natural Cycles

No phase Interventional Infertility Female Frozen Embryo Transfer (FET)

For patients and families

In plain language

An automatic summary of structured registry data. It is an orientation aid, not a substitute for the official protocol or a physician assessment.

What is being studied
The protocol lists: Letrozole (Aromatase Inhibitors), Choriogonadotropin alpha (r-hCG), Progesterone.
Who it may be relevant to
Registry conditions: Infertility Female, Frozen Embryo Transfer (FET). Basic parameters: 18 years — 40 years · Female.
What needs checking
Age, condition and sex are only basic indicators. Prior treatment, laboratory values and other mandatory requirements appear in the eligibility criteria below.
Where it takes place
Serbia
Next step
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Official title

FET-LET-2x2: A Randomized Open-Label 2×2 Factorial Trial Comparing Clinical Pregnancy Rates After Frozen Embryo Transfer in True and Modified Natural Cycles With and Without Aromatase Inhibitors

Overview

The goal of this clinical trial is to learn whether different natural approaches to preparing the uterus for frozen embryo transfer (FET) can improve pregnancy success in women undergoing in vitro fertilization (IVF) treatment. The main questions it aims to answer are: 1. Is a completely natural menstrual cycle more successful than a natural cycle in which ovulation is triggered with medication when preparing for frozen embryo transfer? 2. Does taking a medication called letrozole at the beginning of the cycle improve pregnancy success compared to not taking it? Researchers will compare four different approaches to see which one results in the highest chance of achieving a clinical pregnancy, confirmed by ultrasound. Participants will: * Be randomly assigned to one of four groups * Undergo monitoring with ultrasound and blood hormone tests during their menstrual cycle * In some groups, take letrozole tablets for a few days early in the cycle * In some groups, receive a hormone injection to help control the timing of ovulation * Undergo frozen embryo transfer at the appropriate time * Receive standard hormonal support after embryo transfer * Researchers will compare four different approaches to see which one results in the highest chance of achieving a clinical pregnancy, confirmed by ultrasound.

Interventions

  • Drug Letrozole (Aromatase Inhibitors)
    Letrozole 2.5 mg administered orally twice daily from cycle days 3-7 during the early follicular phase.
  • Drug Choriogonadotropin alpha (r-hCG)
    Recombinant human chorionic gonadotropin (hCG) 250 mcg administered subcutaneously to trigger ovulation when follicular and endometrial criteria are met.
  • Drug Progesterone
    Luteal phase support with either vaginal progesterone 200 mg twice daily or subcutaneous progesterone 25 mg once daily, initiated after ovulation (or 2 days after hCG trigger) and continued until 12 weeks of gestation if pregnancy occurs.

Primary outcome measures

  • Clinical Pregnancy Rate [Time frame: Approximately 4-6 weeks after embryo transfer.]
Secondary outcome measures (3)
  • Biochemical Pregnancy Rate [Time frame: Two weeks after embryo transfer.]
  • Implantation Rate [Time frame: Approximately 4-6 weeks after embryo transfer.]
  • Miscarriage Rate [Time frame: Up to 23 weeks of gestation.]

Eligibility criteria

Inclusion criteria

  • Women aged 18 to 40 years
  • Regular menstrual cycles (26-35 days)
  • Scheduled for frozen embryo transfer (FET) in a natural menstrual cycle
  • Normal gynecological ultrasound findings without clinically significant uterine abnormalities
  • Ability to provide written informed consent

Exclusion criteria

  • Use of preimplantation genetic testing (PGT) for the transferred embryo
  • Use of donor oocytes
  • Inadequate embryo survival after thawing, defined as loss of viability in more than 50% of blastomeres
  • Irregular menstrual cycles
  • Presence of clinically significant uterine abnormalities detected by ultrasound
  • Inability or unwillingness to provide written informed consent

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation
Randomized
Model
Factorial
Masking
Open label
Primary purpose
Treatment

Study locations

Serbia · 1 center
  • Specialized Gynecological Hospital "Ferona" Novi Sad — Novi Sad

Identifiers

NCT: NCT07425990 · Ethics Approval No 01-39/8/1

Primary sources (government registries)

View this study on ClinicalTrials.gov ↗