Frozen Embryo Transfer (FET) process step by step

Are there different types of FET?

From our research there appears to be 2 main types of frozen embryo transfer. They are hormone-regulated and natural.

Hormone regulated FET – These cycles use drugs to control your cycle. They ‘turn off’ your embryos and thicken the endometrial lining to encourage implantation of the embryo.

Natural FET – This type of cycles uses your body’s own cycle to time the best point to implant the embryo.

Both have their benefits and risks which we will discuss below. But let’s first look at the process of FET for both types.

Step by step guide to the hormone regulated frozen embryo transfer process

The full hormone regulated cycles take from 6-8 weeks to complete. We won’t go into detail about the drugs, but if you want specific information about them and how they may impact you check out our IVF drug guide. The FET step by step guide below follows the most common process, however this may be slightly adjusted to your specific set of circumstances.

Step 1 – Book your FETThis may sound silly, but you need to call your NHS or private clinic to book in your treatment. You should stop having unprotected sex from the first day of your cycle.

Step 2 – Appointment 1 – Your first appointment will be between day 18 and day 23 of your cycle. You will most commonly meet with a specialist nurse. In this appointment you will discuss the FET process, they will go through the thaw process in detail and explain the risks associated with this. You will be shown how to administer your medication and also be given a treatment timetable. If you have any specific questions, make sure that you take these with you to this appointment. You and your partner will be required to sign consent and thaw consent forms at this stage.

Step 3 – Start first medication – The two most common medications to turn your ovaries off are Prostap or Buserelin. Prostap you will have a single injection and affects of this last about 4 weeks. If you use Buserelin then you will need to inject this on a daily basis. Remember to rotate your injection sites to reduce pain and bruising.

These drugs cause a fall in your oestrogen and the common side effects of this are nausea, headaches, stomach cramps, tiredness, mood swings, mild diarrhoea, bleeding, breast tenderness, hot sweats and vaginal dryness.

You should get your period during this time if you are getting very close to the next step and this hasn’t you should let your clinic know before attending the blood test.

Step 4 – Hormone blood test – The test is looking at the levels of hormones within your body. If the results come back with levels that are expected within your specific circumstances, then you will move to the next step. If they aren’t you may continue with your current medications or they may change them.

step 5 – Start oestrogen medication – After the blood test you will be told to take oestrogen medications, this is to start thickening your lining to make you ready for the embryo transfer and improve the chances of implantation. This medication is usually administered either in tablet or patch form depending upon your clinic.

Step 6 – Transvaginal scan – After 15 days on the oestrogen medications you will be asked to attend your clinic. Here you will have a transvaginal scan. The scan process is a little uncomfortable but not painful. They insert and internal ultrasound probe into your vagina and push gently against the walls to get a clear image of your endometrial lining. They are looking for a lining a minimum of around 7-8mm.

Every woman reacts differently to hormone medications and the scan may identify that you aren’t ready for transfer yet. If this is the case, then your details will be passed to the consultant and new plan will be made. Most commonly this will be to stay on the medications for a longer period and you will have a scan in a few days – weeks’ time to reassess.

You will be given a date for the embryo transfer.

Step 7 – Add progesterone to medication – Once you have the right level of lining thickness you will be given progesterone pessaries. This can be inserted vaginally or rectally. However, on the day of your embryo transfer you may be asked to use it rectally.

The progesterone is used to ensure that your body is ready for pregnancy and can support a pregnancy by maintaining the lining. Some of the side effects that you are possible from progesterone include vaginal irritation and discharge, headaches, chest pains, weakness, fatigue and dizziness.

Step 8 – Embryo thaw and phone call On the morning of your transfer you will receive a call from your embryologist. They will let you know if the embryo/s survived the thaw process and how they are looking and let you know what time to come into the clinic this is usually the same day, but can be up to 3 days post thaw if required.

Step 9 – Attend the clinic for ultrasound scan – Once you arrive at the clinic you will be taken for an ultrasound scan. You will be asked to arrive with a full bladder. It is an abdominal ultrasound and is completely painless. They are looking at the structure, size and shape of your uterus to determine the best position for the transfer catheter.

Step 10 – Embryo transfer – Once this has been completed, you will be asked to repeat your details several times, this is to ensure the right embryos are transferred. You will be taken into a small sterile room; your partner is able to come in with you. You are likely to be shown the embryo on a computer monitor so men the most important job is to get a good photo.

The embryos are sucked into the transfer catheter under microscope by the embryologist and passed to the nurse or doctor doing the procedure. The catheter will be passed through your cervix into the determined place in your uterus. This bit of the procedure isn’t painful, but it can be uncomfortable and feels similar to a smear test.

The embryo(s) are then released into the uterus. The transfer catheter is then re-checked by the embryologist to ensure that the egg has been implanted. After this you are free to go home and rest.

Step 11 – The dreaded TWW – This is often the hardest part of any assisted reproduction technique. During this time, you will be asked to continue taking the progesterone to support your endometrial lining. Often people worry about what they should and shouldn’t be doing during this time. If you are one of those people then check out our surviving the 2-week wait guide.

Step 12 – Pregnancy test – The big day has arrived. This is where things can be different. Some clinics will ask you to do a at home pregnancy on a specific date and they will advise you to stop progesterone treatment after this date if you get a BFN (big fat negative.) However, many clinics will get you in for a proper blood test. If you are not happy just doing an at home test, then many GP’s will do a pregnancy blood test for you.  We really hope you get a BFP!

Step 13 – Outcome – If you were unsuccessful your notes will be discussed internally, and a review meeting will often be scheduled to see if a change of protocol may be of benefit. If you had a positive test then you will be invited to a scan 3 weeks after this positive result to check the heartbeat, position of the pregnancy and the number of babies. This is an important check. After this all being well you will be discharged to regular maternity services.

Natural Frozen embryo transfer process.

The process above is pretty much applicable to the natural version, so we won’t rewrite it here. The key differences are: –

  • You will not take any of the drugs up to the point of embryo transfer however some women will still be advised to use progesterone afterwards to support the lining.
  • The timings will be different as it will be dictated by your natural cycle
  • Natural FET is generally only used when a woman has a regular menstrual cycle.

Natural vs hormone regulated FET in terms of success rates

Much of the latest evidence which can be read here is showing that in those with regular menstrual cycles the clinical pregnancy rate, live birth rates and miscarriage rates are not significantly different with either method.

One 2015 study had key results as follows

Measurement Hormone regulated Natural
Clinical pregnancy rate 38.9% 35.3%
Live Birth rate 35.3% 31.8%
Miscarriage rate 1.2% 1.2%

At first glance these results may seem as though they are fairly significant, however in statistical terms and when the size of the study is included, they aren’t. The conclusion which was drawn from this study was:

In conclusion, based on the results of our study, modified natural cycles should be recommended in FET because they carry numerous advantages and have comparable FET outcomes, at least in patients with regular menstrual cycles.

Special points to know about Frozen Embryo transfers.

There are some important things that you should at least be aware of regarding using frozen embryos.


  • Not all embryos survive the thawing process, about 15% don’t survive the freeze thaw process.
  • You can only store embryos for a maximum of 10 years this is regulated and decided by the HFEA
  • You need to keep your records completely up to date as if the clinic cannot get hold of you and the storage period comes to an end they must allow them to perish.
  • When they were originally frozen you would have told them what you want to happen to them or how they can be used in the event of your death or loss of capacity. If you change your mind or your circumstances change you must let the clinic know.
  • Frozen Embryo transfers are generally less expensive than full IVF cycles at around £1,448 you can find detailed in formation on the Costs of IVF and FET in our article.


Submit a Comment

Your email address will not be published.