Treatments & Services
Frozen Embryo Transfer
What is a frozen embryo transfer (FET)?
FET is the process in which a frozen embryo from a previous IVF treatment cycle is thawed and transferred back into the uterus. It provides the opportunity to become pregnant without having to undergo another cycle of hormone stimulation and egg collection.
Frozen embryo cycles can be undertaken during a natural cycle for women who ovulate regularly. If required, ovulation induction or hormonal therapy can be prescribed to create the correct environment for the embryo to implant. In order to monitor an FET cycle, our nursing team will coordinate any necessary blood tests and ultrasound scans, and with a fertility doctor, will confirm the best day to carry out your FET.
When is an FET recommended?
If you have frozen embryos available they should be considered for transfer first before beginning another fresh IVF cycle, unless there has been a discussion that they should be retained for fertility preservation.
In some situations, it may not have been appropriate to have an embryo transfer in a fresh IVF cycle. In this case, any good quality embryos produced from your fresh cycle are frozen by our embryology team. Reasons for not having a fresh embryo transfer can include:
- If a fresh embryo transfer would have increased your risk of over stimulating (OHSS);
- If you had raised progesterone level prior to egg collection, which alters the environment for embryo implantation;
- If you are awaiting results following PGT-A;
- If you are the recipient of donated eggs; or
- If you are not wanting to get pregnant right away.
Are FET as successful as fresh embryo transfers?
The pregnancy success rate of frozen embryos is similar to that of fresh embryos, making FET’s a reliable and safe option for you. Embryos are snap frozen using a process called vitrification. This process is highly successful, with at least 95% or more of the embryos surviving after thaw.
How are embryos stored?
Embryos chosen for freezing are placed in a special freezing solution and frozen on individual vitrification devices. During the process of vitrification, they are snap frozen in liquid nitrogen.
Your embryos remain frozen and securely stored in specialised tanks under liquid nitrogen, which ensures they remain at a consistently cold temperature. Our storage tanks undergo 24-hour electronic temperature monitoring and are located in a secure and alarmed area only accessible by our Embryology team.
How are embryos thawed and transferred?
The thawing process involves rapidly warming an embryo to 37°C in special solutions that rehydrate the cells of the embryo and remove the solutions that were part of the freezing process. Thawing is typically performed on the morning of the FET, but may be done the day before in some cases.
The transfer procedure is performed by a fertility doctor under ultrasound guidance. The transfer is normally a very simple procedure and is similar to undergoing cervical screening. You will be awake and you can get up straight afterwards to continue with your day. The lining of your uterus will be quite sticky during this time, so the embryo will remain in place. Your partner or support person is always welcome to be present during this procedure.
How long can embryos stay in storage?
Embryos can be kept in storage for future use, provided you continue to pay the annual storage fee. In South Australia, there are currently no restrictions with regards to the length of time that embryos can be stored. At Flinders Fertility, embryos can remain in storage with us until the woman who would undergo the embryo transfer reaches the age of 51 (the average age of menopause). During this time, we send out an annual storage letter to ensure we continue to honour your wishes and inform you as to when the storage time limit is approaching.
What if I want to discontinue storage of my embryos?
If you want to discontinue the storage of your embryos, a discard form will need to be signed by you. Embryo donation can be considered in some cases; however, this requires multiple counselling sessions and thorough consideration in order to explore the topics around donation. You can learn more about your options in our news section.