Embryo freezing is routine at CARE, and with the vitrification technique frozen embryos can get great results. You won’t know whether you have embryos available for freezing until you’re well into your treatment cycle, but we’ll discuss the possibility with you before you start treatment.
You might freeze your embryos because:
Everyone’s different, and we’ll go through all aspects of your treatment to help you decide exactly what’s right for you.
When you’re going through IVF treatment, once we’ve fertilised your eggs we’ll talk to you regularly about how your embryos are developing, and we’ll let you know whether there will be any of the right quality left for freezing. If there are, and you’d like us to store them for you they are frozen in the following steps:
When you’re ready to use your embryos we’ll remove an embryo from storage and carefully warm it. Then, if it’s good enough quality, we’ll prepare it for transfer. We’ll aim to place the embryo into the womb of you or your partner at the right time of the cycle, and timing will depend on the stage of the embryos, i.e whether they’re fertilised eggs, early embryos or blastocysts.
Before embryos are frozen, we ask you to complete consent forms which cover the following:
The maximum period of time is usually 10 years, but this may differ in certain circumstances such as health conditions and what has been agreed with your clinic – you will specify the storage period when you complete your consent forms. Continued storage is conditional on payment of the annual storage fee.
It’s possible for either (or both) partners to withdraw their consent to the use or donation of embryos up to the point of embryo transfer. If there’s a dispute between partners over use or donation, CARE is allowed by law to keep embryos for up to one year (following written notification of consent withdrawal) to allow a ‘cooling off’ period. If the dispute remains unresolved at the end of this time the embryos must be removed from storage.
Frozen embryos can be transferred in two types of treatment cycle: you can undergo treatment in an ‘artificial’ cycle using hormone therapy, or if you ovulate reliably your embryos could be replaced in your natural cycle. The pregnancy rate is unaffected by the choice and is very good with either option.
Artificial FER uses hormones (oestradiol and progesterone) to prepare your uterus in readiness for embryo transfer. A scan is carried out to check your endometrium has responded effectively to the oestradiol. If it has, then progesterone is given which prepares your endometrium to receive the embryo(s). This timing is precise to ensure the day of transfer is optimal for embryo implantation and growth. The advantages of an artificial FER include more predictability, effectiveness in irregular cycles and a shorter time to transfer as no trial cycle is needed.
In natural cycle FERs it is necessary to undertake a ‘trial’ cycle before an actual FER cycle. It must be possible to detect ovulation hormone surge using ovulation predictors, because this sets the day of the embryo transfer – so natural cycle FER is only suitable for women with regular cycles.
Not all embryos can survive the stressful vitrification process used in embryo freezing, which involves the embryos passing through a series of solutions followed by storage in liquid nitrogen at –196C. We expect about 95% of good grade embryos to survive freeze-thawing. Sometimes embryos may lose a few cells but still be considered suitable for embryo transfer, as studies have shown they may still be capable of implanting providing more than half the cells remain intact. The survival and quality of the thawed embryo(s) will be discussed with you at the time of transfer.
This procedure is as safe as using fresh embryos. The main risk is having multiple births (twins or triplets), which can pose health risks to both mum and babies.
If you no longer wish to have treatment but still have embryos in storage, there are several options you may wish to consider: