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

January 29, 2026 updated by: ShangHai Ji Ai Genetics & IVF Institute

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.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

828

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • China
    • Shanghai Municipality
      • Shanghai, Shanghai Municipality, China, 200011
        • Shanghai JiAi Genetics & IVF Institute

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

20 years to 40 years (Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

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

Exclusion Criteria:

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Immediate FET group
FET will be performed in the first menstrual cycle following the stimulated IVF cycle
Procedure: Immediate FET
FET is performed in the first menstrual cycle following the stimulated IVF cycle
Other: Delayed FET group
FET will be performed in the second menstrual cycle following the stimulated IVF cycle
Procedure: Delayed FET
FET is performed in the second menstrual cycle following the stimulated IVF cycle

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
live birth
Time Frame: 1 year after FET
deliveries ≥22 weeks gestation with heartbeat and breath
1 year after FET

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
multiple pregnancy
Time Frame: multiple pregnancy beyond gestation 12 weeks
more than one intrauterine sacs on scanning
multiple pregnancy beyond gestation 12 weeks
ectopic pregnancy
Time Frame: ectopic pregnancy during 12 weeks gestation
pregnancy outside the uterine cavity
ectopic pregnancy during 12 weeks gestation
birthweight of newborns
Time Frame: 1 year after FET
the birth weight of newborns
1 year after FET
positive hCG
Time Frame: 2 weeks after FET
serum β-hCG ≥10 mIU/mL
2 weeks after FET
clinical pregnancy
Time Frame: 6 weeks' gestation
presence of intrauterine gestational sac by trans-vaginal ultrasound at 6 gestational weeks.
6 weeks' gestation
ongoing pregnancy
Time Frame: 12 weeks' gestation
a viable pregnancy beyond 12 weeks' gestation
12 weeks' gestation
implantation rate
Time Frame: 6 weeks' gestation
the number of gestational sacs per blastocyst transferred
6 weeks' gestation
miscarriage
Time Frame: 1 year after FET
a clinically recognized pregnancy loss before the 22 weeks of pregnancy
1 year after FET

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

ShangHai Ji Ai Genetics & IVF Institute

Investigators

  • Study Director: Xiaoxi Sun, Phd, Shanghai JiAi Genetics & IVF Institute

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

May 4, 2020

Primary Completion (Estimated)

June 1, 2026

Study Completion (Estimated)

June 30, 2026

Study Registration Dates

First Submitted

April 29, 2020

First Submitted That Met QC Criteria

April 29, 2020

First Posted (Actual)

May 1, 2020

Study Record Updates

Last Update Posted (Actual)

February 2, 2026

Last Update Submitted That Met QC Criteria

January 29, 2026

Last Verified

May 1, 2025

More Information

Terms related to this study

Other Study ID Numbers

  • JIAI 2020-04

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Individual participant data that underlie the results after deidentification (text, tables, figures, and appendices) and study protocol will be shared.

IPD Sharing Time Frame

Data will be available when beginning 3 months and ending 5 years following article publication.

IPD Sharing Access Criteria

To achieve aims in the approved proposal, researchers who provide a methodologically sound proposal will be shared with. Proposals should be directed to lihe198900@163.com.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ANALYTIC_CODE
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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