Are you considering a frozen IVF cycle? Within fertility there is a lot of talk about freezing your eggs – but what about freezing your embryos? If you are going through the process of IVF, you may be asked if you want to freeze your embryos so you can return to them at a later date. But what does that involve? And what does that process look like? Fertility Nurse, Liz Harrison breaks it all down for you in this helpful blog on frozen IVF cycles.
What is a frozen IVF cycle?
After an IVF cycle some people have extra embryos left over. These embryos can be frozen and be used at a later date, perhaps if treatment has not worked or if you want to have a sibling for a baby you had from an earlier cycle.
Sometimes freezing your extra embryos can lead to a higher chance of success. This is because the embryos would have been created when you were younger – and your egg quality potentially better. For example, perhaps you did your first IVF cycle at 33 and frozen embryos from that round. If you come to do another IVF cycle 4 years later, the embryos that were frozen when you were 33 could be of better quality than those created from a new cycle at 37.
Using frozen embryos can also be beneficial for your own mental and physical health. Going through the process of harvesting fresh eggs can take its toll on you hormonally and emotionally. Whilst using frozen embryos still involves a lot of planning, it does cut out some portions of the IVF cycle and make the process slightly less invasive.
How do you freeze embryos?
Embryos are frozen in liquid nitrogen and are frozen through two different methods, slow frozen and vitrification – both of which are deemed to be safe. The embryos need to be of good quality and can be frozen at different stages of their development – when they’re just a single cell, at the two to eight-cell stage or later in their development (called the blastocyst stage).
What happens during a frozen IVF cycle?
The truth is, it’s not as simple as just “thawing the embryos and ‘popping’ them back into the uterus.” It takes a bit more work, planning and precision… Some clinics may use your natural cycle, but it depends on their protocols and your history. Here I will talk about a medicated cycle and each clinic may do something slightly different.
Down regulation
On day 1 of your cycle, you would phone the clinic. On day 21 of your cycle, you will start taking Buserelin. Buserlin can come as an injection or it can be inhaled. The aim of this drug is to stop you ovulating whilst the lining is prepared.
Down-regulation scan
After two weeks of Buserelin you will attend the clinic for a down-regulation scan. The scan will assess the womb lining of your uterus and see how active your ovaries are. If everything looks fine, you will be able to start your cycle. After your scan you will start to take hormone tablets (oestradiol) to build up your womb lining. You would also continue taking Buserelin, but at a reduced dose.
Follicle tracking scans
After 11-13 days, you will have an ultrasound scan. Your clinic will measure the thickness of your womb lining and the size of any growing follicle. If the womb lining is more than 8 mm and no follicle is visible you are ready for your embryo transfer. If a dominant follicle larger than 14 mm is visible, you will have a blood test to see whether you have ovulated. If you have ovulated, your cycle will be cancelled because of reduced chances of success. If the womb lining is too thin, you will continue taking oestradiol and return after 7 days for a scan. If the womb lining does not thicken your cycle may be cancelled.
Additional hormones
When your womb lining has reached optimum thickness and you are ready for your frozen embryo transfer, you will stop taking Buserelin and will begin to use progesterone (while continuing the oestradiol). This is to help make the womb lining receptive to the embryo(s). The start of progesterone equals luteal day 0.
Thaw and transfer
The embryos are thawed according to your consent. The majority of the embryos tolerate freezing and thawing well, but some may not. Your clinic usually doesn’t call you, but decisions to thaw more might be needed and we therefore ask that you are available on the day of thawing.
What happens if I have frozen embryos and something changes?
Consent is an essential part of fertility treatment and it is incredibly important to think about what will or could happen in your treatment. Frozen embryos contain your DNA and have the potential to become a child – so it’s important that you are explicit about what you would want to happen if something were to happen to you – or if your relationship were to break down. For example, if your partner withdraws their consent then your embryos cannot be used in treatment. Cases have gone to court, sadly a child was born against the father wishes as he did not update his consent forms, the case went to court and the father lost damages.
One of the questions that is asked in the consent form is ‘what you would like to happen to your eggs, sperm or embryos if you were to die or lose the ability to decide for yourself’. This is so clinics know what your wishes are therefore it is paramount that you update your wishes if something changes.
