At IVI we are frequently asked questions about the differences between frozen and ‘fresh’ embryos as part of the process of in vitro fertilisation (IVF). Patients want to know whether to expect the signs and symptoms of pregnancy following the transfer of a frozen embryo to be any different.

In this IVI blog article, we take a look at the implications of frozen embryo use. Why are frozen embryos created in the first place? When and why are they likely to be used, is the resulting pregnancy success rate any different? As for the test, is a pregnancy test after IVF frozen embryo transfer any different from the test following any other IVF procedure? Read on for all you need to know about frozen embryo transfer and the subsequent pregnancy test.

Why do we need frozen embryos?

When a woman who needs fertility treatment goes through a cycle of IVF, it involves a period of hormonal medication that stimulates the ovaries to produce multiple eggs. These are fertilised in the laboratory as part of the normal IVF process. This naturally results in the existence, if there are enough good-quality eggs, of several embryos. Why not just one?

Egg quality

The quality of your eggs declines with age, regardless of how fit and healthy you are. It’s also a fact of life that for many women, by the time they have tried to conceive for a while, sometimes for many years, and decide to opt for fertility treatment, they can be approaching the age where egg quality starts to decline. This is why we need multiple embryos. They can be observed over a few days of development and only the best quality embryo selected for transfer back to the uterus. The fact that we obtain several embryos in just one treatment would increase the number of attempts and the probabilities of getting pregnant. The surplus embryos are frozen in order to improve these pregnancy rates

The time taken by fertility treatment

The most time-consuming aspect of IVF fertility treatment by far is the ovarian stimulation phase, which can take anything from 10 to 15 days usually. It’s therefore a bonus if, in the event of a single embryo transfer failing to result in a pregnancy, we have ‘spare’ frozen embryos in reserve. The patient, when she feels ready, can opt for another attempt, using a previously frozen embryo, without needing to go through the stimulation phase a second time.

When are frozen embryos used?

We have seen that one of the major reasons for using a frozen embryo is in the event of an unsuccessful IVF attempt, but there are other advantages too.

Extending your family

If you had a successful pregnancy after IVF and also have spared good-quality embryos, these can be used at a later time if and when you wish to extend your family. There are some big advantages here.

• You avoid having to go through the ovarian stimulation and egg retrieval phase of IVF, and can move straight to the embryo transfer stage, using your own frozen embryo. This takes off the pressure some patients may feel to start a new cycle quickly after a failed treatment, because time is not on their side. With the ‘safety net’ of some stored frozen embryos, a woman can take all the time she needs to recover, both physically and emotionally, before a new attempt.
• The frozen embryos remain at the same ‘age’ they were when fertilised. Even after an extended period, up to 10 years, you can decide when the time is right for you and your family to have another child. You don’t need to be limited by the biological clock that makes a natural pregnancy increasingly unlikely after the age of around 38 to 40. If you were 35 when your embryos were frozen, that’s how they remain, no matter the age of your uterus.

What are the success rates for fresh and frozen embryos?

Pregnancy success rates between fresh and frozen embryo transfer do not differ significantly. This was not always the case, but improvements in the cryopreservation of embryos and their methods of storage mean that in our clinics at IVI, 95% of embryos survive the thawing process and are suitable for transfer.

At IVI we have an overall success rate of 95% for IVF. This is the cumulative figure for three attempts and includes both frozen and fresh embryo transfer. We publish our success rates in detail, so you can analyse results by type of fertility treatment, as well as other factors such as the age of the patient.

What about the pregnancy test after frozen embryo transfer?

There may be several differences between fresh and frozen embryo transfer, but this is not one of them. The pregnancy test after an IVF frozen embryo transfer is identical to the test following any IVF procedure. Following embryo transfer, a few things need to happen, regardless of whether the embryo is fresh or frozen.

• The embryo needs to implant in the lining of the womb. This takes the same few days whether your conception is natural or the result of IVF using a fresh or frozen embryo. The implantation can be accompanied by slight spotting or cramping, but these symptoms cannot be taken as a sure sign of pregnancy. When you have had an assisted reproduction treatment, they could be the result of progesterone supplements, which are a necessary part of the treatment.
• After implantation, the embryo starts to secrete the hormone human chorionic gonadotropin (hCG), with levels steadily increasing in the early weeks. This is the hormone that normal home pregnancy tests measure in the urine. However, your hormone levels can be affected by the hormonal medication needed, even though the medication protocol used for a frozen embryo transfer would be different from that used in a fresh IVF cycle. For this reason, a home kit can be unreliable and so it’s essential to have a blood test carried out by a qualified and experienced gynaecologist.

Contacting us at IVI

Would you like to know more about how a frozen embryo transfer? Do get in touch with us. You can use our online contact form, or watch our video to get an idea of what to expect from your first visit to IVI.