Frozen embryo transfer: the timeline and when to test
A frozen embryo transfer (FET) is the transfer to the womb of an embryo that was created and frozen in an earlier IVF cycle. This guide sets out the natural and medicated ways of preparing for it, the steps from thaw to transfer, how it compares with a fresh transfer, and when to test.
Last updated
Medically reviewed by Dr Mary Davidson, Reproductive endocrinologist, checked on
Seek help now if you have any of these symptoms
Bleeding and cramping are common in early pregnancy and often do not mean miscarriage. The symptoms below, however, need to be assessed straight away.
- Soaking two or more sanitary pads per hour, or passing large clots
- Severe lower abdominal pain, especially on one side
- Pain at the tip of the shoulder
- Dizziness, fainting, or collapse
- Signs of shock — pale, clammy, rapid heartbeat, breathlessness
- Pain on opening bowels, or bladder or bowel changes
- Feeling very unwell, or feverish
Showing routes for United States.
The HFEA lists ectopic pregnancy among the risks of IVF (HFEA, "In vitro fertilisation (IVF)", 2026). The NHS treats bleeding in pregnancy as an emergency when it comes with severe abdominal pain, pain in the shoulder, or feeling sick, faint or dizzy, and when it is heavy enough to soak a period pad soon after you put it on (NHS, "Vaginal bleeding in pregnancy", 2026). In the UK, call the emergency number or go to A&E, the hospital emergency department; in the US, call the emergency number or go to the nearest emergency room. The box above shows the emergency and urgent numbers for where you are, and get help now lists the other symptoms that need checking straight away.
What is a frozen embryo transfer?
In IVF, several good-quality embryos are often created. The HFEA says it is normally best practice to freeze the ones not transferred, because putting two embryos back increases the chance of twins or triplets, and that frozen embryos can be used later if the first cycle is unsuccessful or you want another baby (HFEA, "In vitro fertilisation (IVF)", 2026). The NHS says suitable leftover embryos may be frozen for future attempts, and that the clinic will explain any costs, such as storage (NHS, "IVF", 2025). An IVF frozen embryo transfer is the later use of one of those embryos.
The embryos can be frozen at different stages: as a single cell, at the two to eight cell stage, or later, at the blastocyst stage. They are placed in a solution that protects the cells from ice crystals and frozen, mostly by a fast-freezing technique called vitrification, then kept in tanks of liquid nitrogen (HFEA, "Embryo freezing", 2026). In the UK the law allows embryos to be stored for use in treatment for up to 55 years from when they were first stored, as long as consent is renewed every 10 years (HFEA, "Embryo freezing", 2026).
Frozen embryo transfer protocol: natural and medicated cycles
The womb lining has to be ready to receive the embryo when it is thawed. The HFEA says the exact procedure varies with your circumstances and your clinic, and that the first steps depend on whether you ovulate regularly (HFEA, "Embryo freezing", 2026). That gives two main kinds of frozen embryo transfer cycle.
Natural cycle
If your periods are regular, the HFEA says your doctor may suggest transferring the embryo with no fertility drugs. Ultrasound scans may be used to check the lining of the womb, and urine or blood tests to find when you ovulate, which shows that the lining will be ready (HFEA, "Embryo freezing", 2026).
Medicated cycle
If your periods are irregular, or you do not have them, the HFEA says your doctor may suggest drugs to suppress your natural cycle and trigger a false period, followed by medication to prepare the womb lining (HFEA, "Embryo freezing", 2026). A medicated frozen embryo transfer timeline is therefore set by the clinic's medication schedule rather than by your own ovulation. Which medicines are used, and at what doses, is for your clinic to explain.
Frozen embryo transfer timeline
The frozen embryo transfer process, step by step, as the HFEA and the NHS describe it:
- Consent and storage. Embryos are stored only with the consent of both people who provided the eggs and sperm, and that consent covers how long they are kept and how they may be used (HFEA, "Embryo freezing", 2026).
- Preparing the cycle. A natural cycle tracked by scans and ovulation tests, or a medicated cycle that suppresses your own and prepares the lining, as above.
- Thaw. When the timing is right, the clinic's embryologist thaws the embryos (HFEA, "Embryo freezing", 2026).
- Transfer. Usually one embryo is transferred to the womb; the HFEA says three may be transferred only in exceptional circumstances if you are over 40 (HFEA, "Embryo freezing", 2026). The transfer itself is the same short procedure as a fresh embryo transfer.
- The test date. You are given a date to take a pregnancy test (HFEA, "In vitro fertilisation (IVF)", 2026).
The number of days between the steps depends on your cycle and your clinic, and the sources read for this page give no fixed count. The frozen embryo transfer calendar your clinic gives you is the one to follow.
Preparing for a frozen embryo transfer
Preparing for frozen embryo transfer is mostly the clinic's schedule: the scans or tests of the cycle, any medication, and the consent already in place. Before embryos are frozen, the HFEA says you are tested for infectious diseases such as HIV and hepatitis (HFEA, "Embryo freezing", 2026). The ASRM guideline on the transfer itself found no benefit from bed rest after a transfer, in 14 studies, and fair evidence that acupuncture around the transfer does not improve live-birth rates (ASRM, "Performing the embryo transfer: a guideline", 2017). Your clinic's own instructions are the ones to follow.
Fresh vs frozen embryo transfer
The HFEA addresses the questions people ask most when comparing the two (HFEA, "Embryo freezing", 2026):
- Safety. Using frozen embryos is just as safe as using fresh ones. The main risk is a multiple birth, which can be reduced by transferring a single embryo.
- Thawing. Not all embryos survive freezing and thawing, and very occasionally none do. Embryos that survive often lose a cell or two, and in many cases recover and continue to develop; the clinic tells you whether an embryo is suitable to transfer.
- Time in storage. The HFEA says there is no evidence that embryos are affected by how long they are frozen, while also noting that research continues and there is not enough evidence to be sure whether longer storage affects viability.
In a fresh transfer, the womb is prepared within the same cycle as the egg collection; in a frozen transfer, it is prepared in a later cycle, natural or medicated. That is the practical difference in the timeline.
When to test after a frozen embryo transfer
You will be given a date for a pregnancy test, and the HFEA advises not testing early because the result may be false (HFEA, "In vitro fertilisation (IVF)", 2026). The NHS gives the test date after a transfer as around 16 days later (NHS, 2025). A urine pregnancy test after a frozen embryo transfer, or a blood test at the clinic, is taken on that date. The full comparison of test days, and what a blood hCG test measures, is in the guide to embryo transfer, and why a single hormone number cannot be judged alone is explained under hcg levels.
Your due date after a frozen embryo transfer
A frozen embryo transfer due date is worked out exactly as one after a fresh transfer. ACOG says the due date after IVF is set from the age of the embryo and the date of transfer: 261 days after the transfer of a day-5 embryo and 263 days after a day-3 embryo (ACOG Committee Opinion 700, 2017). Whether the embryo was frozen makes no difference to the count. The FET due date calculator on this site, the IVF due date calculator, does the arithmetic as a frozen embryo transfer calculator: enter the transfer date and the embryo's age, and choose frozen. The pregnancy week calculator then shows how many weeks along you are on any day.
Frozen embryo transfer success rate
The HFEA says success rates for IVF using frozen embryos have been increasing year on year, and publishes the latest national figures on its research and data pages (HFEA, "Embryo freezing", 2026). It also says success depends on the woman's age and the cause of infertility, and advises talking to your doctor about your own chances (HFEA, "In vitro fertilisation (IVF)", 2026). This page prints no rate for a first frozen embryo transfer or any other, because a single figure says little about one person's chances.
This guide is information, not a diagnosis or a recommendation of treatment, and it is no substitute for your own clinician. See the medical disclaimer.
Sources
- Human Fertilisation and Embryology Authority. Embryo freezing. HFEA, 2026.
- Human Fertilisation and Embryology Authority. In vitro fertilisation (IVF). HFEA, 2026.
- NHS. IVF. nhs.uk, 2025.
- Practice Committee of the American Society for Reproductive Medicine. Performing the embryo transfer: a guideline. Fertility and Sterility 107(4): 882-896, 2017.
- American College of Obstetricians and Gynecologists, American Institute of Ultrasound in Medicine and Society for Maternal-Fetal Medicine. Committee Opinion No. 700: Methods for Estimating the Due Date. ACOG, 2017.
- NHS. Vaginal bleeding in pregnancy. nhs.uk, 2026.
Frequently asked questions
What is a frozen embryo transfer?
The transfer to the womb of an embryo that was frozen after an earlier IVF cycle. The embryo is thawed on the day, and usually one is transferred (HFEA).
On which day of the cycle is a frozen embryo transfer done?
There is no single day. In a natural cycle the clinic times the transfer from ovulation, found with urine or blood tests, and checks the womb lining with scans. In a medicated cycle the natural cycle is suppressed and the lining is prepared with medication, so the clinic sets the day. Your clinic gives you the date.
How long after egg retrieval is a frozen embryo transfer?
There is no fixed interval. The embryos are stored until they are wanted: in the UK the law allows storage for up to 55 years, with consent renewed every 10 years (HFEA). The timing of the transfer follows the cycle it is planned in, not the date the eggs were collected.
Is a frozen embryo transfer as safe as a fresh one?
The HFEA says using frozen embryos is just as safe as using fresh ones, and that the main risk is a multiple birth, which transferring one embryo reduces.