Egg/Sperm Freezing

Egg and sperm freezing is a fertility preservation method that stores a person's eggs or sperm at very low temperatures so they can be used to start a pregnancy at a later date.

For egg freezing, the ovaries are first stimulated with hormone injections to produce multiple eggs. Those eggs are then collected and rapidly cooled using a process called vitrification (flash-freezing), which prevents damaging ice crystals from forming inside the cells. The frozen eggs can be stored for years. When the person is ready to try for a pregnancy, the eggs are warmed, fertilised with sperm in a laboratory, and the resulting embryo (fertilised egg) is placed into the uterus. For sperm freezing, a semen sample is collected, checked for quality, mixed with a protective fluid called a cryoprotectant (a substance that shields cells from freezing damage), and then stored in liquid nitrogen at extremely low temperatures until needed.

Egg and sperm freezing is used whenever someone wants to protect their ability to have biological children in the future, whether for medical reasons or personal choice. Doctors commonly recommend it in the following situations:

• Before cancer treatment such as chemotherapy (drug treatment that kills fast-growing cells) or radiotherapy (radiation treatment), which can damage eggs or sperm.
• Before surgery that may affect the ovaries, uterus, or testicles.
• For people with conditions that reduce fertility over time, such as endometriosis (tissue similar to the uterus lining growing outside the uterus) or premature ovarian insufficiency (early decline in ovary function).
• For people with a genetic condition that could be passed to children, who plan to use pre-implantation genetic testing before embryo transfer.
• For transgender individuals who wish to preserve fertility before starting hormone therapy or gender-affirming surgery.
• For people who are not yet ready to have children but want to keep that option open, including those who have not yet found a partner.

Egg freezing is generally not recommended in certain situations. Your doctor will assess whether it is suitable for you based on your age, ovarian reserve (the remaining supply of eggs in the ovaries), and overall health.

• Very low ovarian reserve, where stimulation is unlikely to produce enough eggs to make storage worthwhile.
• Active hormone-sensitive cancers, where ovarian stimulation may be unsafe without specialist guidance.
• Certain medical conditions that make anaesthesia or egg retrieval too risky.

Egg and sperm freezing is generally considered safe, but like any medical procedure, it carries some risks, particularly on the egg-freezing side which involves hormone stimulation and a minor surgical step.

• Ovarian hyperstimulation syndrome or OHSS (a condition where the ovaries over-respond to hormones, causing bloating, abdominal pain, and in rare cases fluid buildup): this is the most common concern and is usually mild.
• Discomfort, bruising, or bleeding at the injection sites during the stimulation phase.
• Pelvic discomfort or cramping after the egg retrieval procedure.
• Minor risk of infection after egg retrieval.
• Small risk of injury to nearby structures such as blood vessels or the bowel during egg retrieval, though this is uncommon.
• The eggs or sperm may not survive the freezing and thawing process, meaning fewer usable eggs or sperm than expected.
• There is no guarantee that frozen eggs will lead to a successful pregnancy when used in the future; the chances depend on factors such as age at the time of freezing and the number of eggs stored.
• Sperm freezing carries very little physical risk, as it involves only providing a semen sample.

Preparation for egg freezing takes several weeks and involves tests, hormone injections, and a short procedure. Sperm freezing requires much less preparation. Your care team will give you a personalised plan, but the general steps are as follows.

Before egg freezing begins, your doctor will usually run a series of assessments. These typically include a blood test to check your hormone levels and ovarian reserve (how many eggs your ovaries still hold), an ultrasound (USG) to look at your ovaries, and a general health check. If sperm is being frozen, the semen will be analysed in a laboratory to assess the number, shape, and movement of the sperm. Both partners, if applicable, may also be tested for certain infectious diseases as required by most fertility clinics.

For egg freezing, you will be advised to avoid smoking and limit alcohol during the stimulation phase, as these can affect egg quality. Your doctor will guide you on whether any regular medications need to be paused. On the day of egg retrieval, you will usually be asked to fast (not eat or drink) for several hours beforehand because a light sedative or anaesthetic (a medication that makes you drowsy or puts you to sleep briefly) is used.

The egg freezing process unfolds in the following steps:

• Ovarian stimulation: you self-inject hormone medications daily for roughly ten to fourteen days to encourage your ovaries to produce multiple eggs. The exact duration depends on how your body responds.
• Monitoring: you visit the clinic regularly for blood tests and USG scans so the doctor can track how your eggs are developing and adjust the hormone doses if needed.
• Trigger injection: when the eggs are ready, a final hormone injection is given to mature them before retrieval.
• Egg retrieval: under light sedation or anaesthesia, a doctor uses a thin needle guided by USG to collect the eggs through the vaginal wall. The procedure usually takes around fifteen to thirty minutes.
• Freezing: the retrieved eggs are assessed by an embryologist (a specialist in eggs, sperm, and embryos) and those suitable for storage are vitrified and placed in a storage tank filled with liquid nitrogen.
• For sperm freezing: a semen sample is produced, usually on the same day as collection. The sample is processed in the laboratory, mixed with a cryoprotectant, and frozen in multiple small portions called straws.

After egg retrieval, most people go home the same day once the sedation has worn off and the care team is satisfied they are well. Recovery is usually quick, but there are important things to be aware of in the days that follow. Sperm freezing requires no physical recovery time.

• You will be monitored in the clinic for a few hours after egg retrieval before being allowed to go home. You will need someone to accompany you, as you should not drive after sedation.
• Mild cramping, bloating, and light spotting (minor vaginal bleeding) are common in the first day or two after egg retrieval and usually settle on their own.
• Rest for the remainder of the day of the procedure. Most people feel well enough to return to normal daily activities within one to three days, though your doctor will advise based on how you feel.
• Avoid strenuous exercise, heavy lifting, and sexual intercourse for a period after retrieval; your doctor will give specific guidance on how long.
• Watch for signs of OHSS (ovarian hyperstimulation syndrome), which can develop in the days after stimulation. Symptoms to report promptly include severe abdominal pain, significant bloating, nausea, vomiting, or difficulty breathing.
• A follow-up appointment is usually arranged to discuss how many eggs were successfully frozen and to answer your questions.
• You will also need to discuss the storage arrangement with your clinic, including how long your eggs or sperm will be stored, annual storage consent requirements, and what your wishes are in various future scenarios.
• When you are ready to use your frozen eggs in the future, you will go through a separate process involving egg warming, fertilisation, and embryo transfer, which your fertility specialist will explain at that time.