What is egg freezing?
A woman’s chance of conceiving naturally falls as she gets older because the quality and number of her eggs drops. Egg freezing is an attempt to preserve a woman’s fertility by freezing the eggs when she is young and the eggs are of higher quality, so she can try to have a family at a later date. It involves collecting a woman’s eggs, freezing them and then thawing them later on so they can be used in fertility treatment.
Who may want to consider egg freezing?
Cancer patients whose treatment will destroy the ovaries;
Patients who need surgical or other treatments for a medical disease that will destroy the ovaries;
Healthy women who may wish to preserve their fertility by storing eggs when they are young. This is often called elective or social egg freezing.
What does egg freezing involve?
In order to collect more eggs, fertility drugs are used to stimulate the ovaries. There are different stimulation protocols. The most commonly used is the antagonist protocol.
The woman takes daily hormone injections in the beginning of her cycle to boost follicle or egg growth. She will be taught how to give the injections by herself, or she can arrange injections to be done at the clinic. The hormone injections are to be done every day for around 8 to 10 days, depending on how fast the follicles grow. During this period, she will be asked to attend the clinic 2 to 4 times to check the growth of the follicles by ultrasound scans. Blood may be taken to check hormone levels if necessary. Another injection drug, known as an antagonist, is added in the latter part of the stimulation period to prevent the eggs from being released too soon. When the eggs are ready, an ovulation trigger injection is given to complete the final maturation of the eggs and egg collection can be arranged.
This protocol is the most suitable one for the majority. However, some women such as cancer patients may need adjustments according to their individual condition. The doctor will decide on the most appropriate protocol for the woman.
Egg collection (Figure 1)
The eggs will be collected from the ovaries about 34-36 hours after the ovulation trigger injection. This is performed in Hong Kong Assisted Reproduction Centre (the IVF centre) with the help of an ultrasound scanner. An ultrasound probe is inserted into the vagina to identify the follicles. A thin needle is then inserted into an ultrasound guide to go through the vagina and into the follicles to retrieve the eggs. The eggs are removed from the follicles through a needle connected to a suction device.
The woman can choose to have either local anaesthesia (LA) or monitored anaesthetic care (MAC) for the egg collection procedure. If the woman chooses to have LA, she will be awake during the entire procedure. A local anaesthetic drug will be injected inside the vagina to reduce the pain level during the egg collection. Alternatively, MAC can be given by an anaesthetist who will be giving her anaesthetic drugs via a drip placed at the back of her hand, and she will be sleeping through.
The whole procedure will usually take around 30-45 minutes. After the egg collection, the woman should rest in the IVF centre, and her condition including blood pressure and pulse will be monitored. If everything goes well, she can go home 2 hours after the procedure, accompanied by an adult. she will need a day off on the day of the egg collection, but can return to work the next day.
At this point, instead of mixing the eggs with sperms as in IVF treatment, a cryoprotectant (freezing solution) will be added to protect the eggs. The eggs will then be frozen by vitrification (rapid freezing) and stored in tanks of liquid nitrogen.
What happens when the woman wants to use her eggs?
When the woman is ready to have a baby, the eggs are thawed and used in in-vitro fertilization and embryo transfer (IVF) treatment. The thawed eggs must be fertilized using a technique called intracytoplasmic sperm injection (ICSI) whereby a single sperm is injected into an egg to assist fertilization, as the freezing process makes the outer coating around the eggs tougher and sperms may be unable to penetrate it naturally under IVF. The resulting embryo(s) will be transferred to the woman’s womb. The aim is that the embryo(s) will develop into a baby / babies.
In Hong Kong, when the woman wishes to use her stored eggs for IVF treatment, she must be legally married and infertile.
How long can the eggs be stored for?
Currently if the woman is storing eggs for social reasons, they can only remain in storage for up to a maximum of 10 years. Women in certain circumstances such as cancer patients can store their eggs for 10 years or up to when they are 55 years old, whichever is later.
When should a woman freeze her eggs?
The stored eggs may not bring about a pregnancy. The age at which the woman freezes her eggs is key to your chance of eventually having a baby. Doctors say the best time is during her 20s and early 30s, as the quality of her eggs declines after the age of 35. But if the woman freezes her eggs when you are 20, she is less likely to ever need to use them because she may conceive naturally. Secondly, she will only be able to use them in IVF treatment up until she is 30. On the other hand, if the woman decides to freeze her eggs in her late 30s, her fertility and ovarian reserve are already in decline. she may have less eggs collected in any cycle and her chance of these eggs leading to a successful pregnancy is lower. She may therefore need more than one cycle of treatment to collect the preferred number of eggs for storage so as to increase her chance of having a child or children from the stored eggs in the future.
We work in collaboration with Hong Kong Assisted Reproduction Centre (HKARC) to provide egg freezing service. HKARC is an IVF centre specialized in assisted reproduction technology treatments. At HKARC, the eggs are frozen with the latest state-of-the-art vitrification method, which is better than the old-fashioned slow freezing method. Vitrified eggs have a higher survival rate when the eggs are thawed, and hence a higher chance of bringing about a pregnancy.