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IVFFETNCT04371783

A Randomized Trial Comparing the Live Birth Rate of Immediate Versus Delayed FET Following a Freeze-all Strategy

A study testing Immediate FET and Delayed FET in people with IVF and Frozen Embryo Transfer, run by ShangHai Ji Ai Genetics & IVF Institute at 1 site in China.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record
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Trial summary

This randomized trial we aim to compare the live birth rate of immediate versus delayed FET replacing a single blastocyst in the first FET of the first stimulated IVF cycle following. Read more about this study

Who is it for?
Ages 20 to 40 years, women only
Conditions the study is for
IVF, Frozen Embryo Transfer
What is being tested?
Immediate FET and Delayed FET
Type of treatment
Surgery or procedure
Could I receive a placebo?
No, everyone receives an active treatment
How many people
828 participants
Where
1 siteChina
Study dates
4 May 2020to 30 Jun 2026
Phase
Interventional
Are there results?
Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 20 to 40 years
  • Women only
  • No healthy volunteers
  • Adult

Who may be able to join

  • Women aged 20-40 years at the time of IVF/ICSI
  • Women undergoing their first FET of the first IVF cycle following a freeze-all strategy
  • Undergoing IVF with GnRH antagonist
  • At least one frozen blastocyst

Who cannot join

  • Severe ovarian hyperstimulation syndrome during the first IVF/ICSI cycle
  • Preimplantation genetic testing
  • Use of donor oocytes
  • Presence of untreated hydrosalpinx or endometrial polyp on scanning during ovarian stimulation

Trial locations and contacts

1 site in 1 country.

China1 site

  • Shanghai JiAi Genetics & IVF Institute

    Shanghai, Shanghai Municipality, 200011

Other trials in China

About this study

Official title: A Randomized Trial Comparing the Live Birth Rate of Immediate Versus Delayed Frozen Embryo Transfer (FET) Replacing a Single Blastocyst in the First FET of the First Stimulated IVF Cycle Following a Freeze-all Strategy

This randomized trial we aim to compare the live birth rate of immediate versus delayed FET replacing a single blastocyst in the first FET of the first stimulated IVF cycle following. The hypothesis is that the live birth rate of the immediate FET is higher than the delayed FET replacing a single blastocyst in the first FET of the first stimulated IVF cycle following a freeze-all strategy. Women will undergo IVF/ICSI in the centre as clinically indicated. Standard ovarian stimulation with gonadotrophins in a Gonadotrophin releasing hormone (GnRH) antagonist protocol will be employed. Hormone replacement treatment (HRT) will be used in subsequent FET cycles. On Day 3 of the menstrual cycle, we will measure the anxiety levels using the Chinese State-Trait Anxiety Inventory and serum E2, cortisol levels will be checked on the same day.

Recruited women having the first FET cycle following a freeze all strategy will be randomly assigned on the day of blastocyst(s) freezing according to a computer-generated randomization list into one of the following two groups.

Being tested
Immediate FET, Delayed FET

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • Immediate FETProcedure or surgery

    FET is performed in the first menstrual cycle following the stimulated IVF cycle

  • Delayed FETProcedure or surgery

    FET is performed in the second menstrual cycle following the stimulated IVF cycle

Study groups in NCT04371783
Study groupRoleWhat they receive
Immediate FET groupOtherFET will be performed in the first menstrual cycle following the stimulated IVF cycle
Receives: Procedure: Immediate FET
Delayed FET groupOtherFET will be performed in the second menstrual cycle following the stimulated IVF cycle
Receives: Procedure: Delayed FET

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. live birth

    deliveries ≥22 weeks gestation with heartbeat and breath

    Measured: 1 year after FET

Secondary outcomes (8)

  1. positive hCG

    serum β-hCG ≥10 mIU/mL

    Measured: 2 weeks after FET

  2. clinical pregnancy

    presence of intrauterine gestational sac by trans-vaginal ultrasound at 6 gestational weeks.

    Measured: 6 weeks' gestation

  3. ongoing pregnancy

    a viable pregnancy beyond 12 weeks' gestation

    Measured: 12 weeks' gestation

  4. implantation rate

    the number of gestational sacs per blastocyst transferred

    Measured: 6 weeks' gestation

  5. miscarriage

    a clinically recognized pregnancy loss before the 22 weeks of pregnancy

    Measured: 1 year after FET

  6. multiple pregnancy

    more than one intrauterine sacs on scanning

    Measured: multiple pregnancy beyond gestation 12 weeks

  7. ectopic pregnancy

    pregnancy outside the uterine cavity

    Measured: ectopic pregnancy during 12 weeks gestation

  8. birthweight of newborns

    the birth weight of newborns

    Measured: 1 year after FET

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted1 May 2020
  2. Study start4 May 2020
  3. Primary completion1 Jun 2026 (estimated)
  4. Study completion30 Jun 2026 (estimated)

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Masking
None (open label)
Enrolment
828 participants (estimated)
IDs, dates and publications
ClinicalTrials.gov ID
NCT04371783
Sponsor's protocol ID
JIAI 2020-04
Acronym
FET
Status last verified
May 2025
First submitted
29 Apr 2020
Last updated
2 Feb 2026
Results posted
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
Yes: Individual participant data that underlie the results after deidentification (text, tables, figures, and appendices) and study protocol will be shared.

Publications

  • Doody KJ. Cryopreservation and delayed embryo transfer-assisted reproductive technology registry and reporting implications. Fertil Steril. 2014 Jul;102(1):27-31. doi: 10.1016/j.fertnstert.2014.04.048. Epub 2014 Jun 4.

    PubMed 24907917

  • Shapiro BS, Daneshmand ST, Garner FC, Aguirre M, Hudson C, Thomas S. Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen-thawed embryo transfer in normal responders. Fertil Steril. 2011 Aug;96(2):344-8. doi: 10.1016/j.fertnstert.2011.05.050. Epub 2011 Jul 6.

    PubMed 21737072

  • Venetis CA, Kolibianakis EM, Bosdou JK, Lainas GT, Sfontouris IA, Tarlatzis BC, Lainas TG. Estimating the net effect of progesterone elevation on the day of hCG on live birth rates after IVF: a cohort analysis of 3296 IVF cycles. Hum Reprod. 2015 Mar;30(3):684-91. doi: 10.1093/humrep/deu362. Epub 2015 Jan 12.

    PubMed 25586787

  • Santos-Ribeiro S, Polyzos NP, Lan VT, Siffain J, Mackens S, Van Landuyt L, Tournaye H, Blockeel C. The effect of an immediate frozen embryo transfer following a freeze-all protocol: a retrospective analysis from two centres. Hum Reprod. 2016 Nov;31(11):2541-2548. doi: 10.1093/humrep/dew194. Epub 2016 Sep 8.

    PubMed 27609984

  • Santos-Ribeiro S, Siffain J, Polyzos NP, van de Vijver A, van Landuyt L, Stoop D, Tournaye H, Blockeel C. To delay or not to delay a frozen embryo transfer after a failed fresh embryo transfer attempt? Fertil Steril. 2016 May;105(5):1202-1207.e1. doi: 10.1016/j.fertnstert.2015.12.140. Epub 2016 Jan 21.

    PubMed 26806686

  • Lattes K, Checa MA, Vassena R, Brassesco M, Vernaeve V. There is no evidence that the time from egg retrieval to embryo transfer affects live birth rates in a freeze-all strategy. Hum Reprod. 2017 Feb;32(2):368-374. doi: 10.1093/humrep/dew306. Epub 2016 Dec 16.

    PubMed 27986819

  • Volodarsky-Perel A, Eldar-Geva T, Holzer HE, Schonberger O, Reichman O, Gal M. Cryopreserved embryo transfer: adjacent or non-adjacent to failed fresh long GnRH-agonist protocol IVF cycle. Reprod Biomed Online. 2017 Mar;34(3):267-273. doi: 10.1016/j.rbmo.2016.11.013. Epub 2016 Dec 16.

    PubMed 28041829

  • Higgins C, Healey M, Jatkar S, Vollenhoven B. Interval between IVF stimulation cycle and frozen embryo transfer: Is there a benefit to a delay between cycles? Aust N Z J Obstet Gynaecol. 2018 Apr;58(2):217-221. doi: 10.1111/ajo.12696. Epub 2017 Sep 14.

    PubMed 28905357

  • Li H, Zhang W, Chen J, Lu X, Li L, Sun X, Ng EH. Immediate versus delayed single blastocyst transfer following the first stimulated IVF cycle in the freeze-all strategy: a study protocol for a randomised controlled trial. BMJ Open. 2024 May 8;14(5):e081018. doi: 10.1136/bmjopen-2023-081018.

    PubMed 38719320

Questions about this trial

What is this clinical trial studying?

A study testing Immediate FET and Delayed FET in people with IVF and Frozen Embryo Transfer, run by ShangHai Ji Ai Genetics & IVF Institute at 1 site in China.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 4 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 2 Feb 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in China. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

live birth (time frame: 1 year after FET). It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04371783, which also lists 9 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Feb 2026.

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