Gynaecology
Delaying parenthood: Two Mediclinic experts explain the process of freezing human eggs and embryos.
What to know before you freeze your eggs
Struggling to conceive? Want to delay parenthood? Egg freezing, known as oocyte cryo preservation or cryo conservation, involves retrieving a woman’s eggs from her ovaries, freezing them and storing them for later use.
What is egg freezing?
Egg freezing can be part of the vitro fertilisation (IVF) process, explains Dr Kasturi Moodley, an obstetrician and gynaecologist at Mediclinic Pietermaritzburg and the Midlands Fertility Health Centre. You can freeze your eggs now and choose to undergo IVF years later – or not at all. Likewise, IVF can be done without using frozen eggs.
“IVF is generally recommended for a patient or couple in three main situations," she says. "First, when both of the woman’s fallopian tubes are blocked. Second, when artificial insemination – also known as intrauterine insemination or IUI – has failed to achieve pregnancy. And third, when the patient's age means the less invasive and less expensive IUI treatment is unlikely to be successful. IVF may also be recommended if there is a problem with the man’s sperm.”
Why people choose to freeze their eggs or embryos
Egg freezing may be considered for various personal, medical or social reasons – for example, when a woman isn’t ready to start a family, is undergoing cancer treatment, or wants to preserve her fertility for the future. The decision to freeze eggs or embryos depends on individual circumstances and goals, and is best made in consultation with a fertility specialist. Cancer treatment can be quite aggressive and targets and destroys rapidly dividing cells.
“Some women in their 20s or early 30s may come to us for egg freezing because they want to delay having children due to work responsibilities or their desire to climb up the corporate ladder,” Dr Moodley adds.
In general, it’s preferable to freeze embryos rather than eggs, she says. “Embryos are more amenable to the freezing process, while eggs are little more vulnerable.”
The process of freezing eggs and embryos
Dr Moodley explains that IVF involves three phases.
Phase 1: Stimulation via injections, given to a woman 14 days from the day of her period, to recruit as many follicles in her ovaries as possible. “We track the development of the egg-containing sacs using ultrasound scans,” explains Dr Moodley. “When they appear ready, we give an injection that triggers the release of the eggs. Thirty-six hours later, we can safely retrieve those eggs from the ovaries.”
Phase 2: The woman comes into the hospital and is given medication to make her drowsy and comfortable. Using a thin needle attached to an ultrasound probe that's inserted through the vagina, the obstetrician-gynaecologist draws out the fluid from each egg-containing sac.
This fluid is then examined under a microscope by a laboratory specialist called an embryologist, who searches through it to find the eggs.
Any eggs found are carefully removed and placed in a special laboratory dish. For women who only want to freeze their eggs for future use, the eggs are then dried out and frozen in the laboratory.
If a patient is going through a full IVF treatment, the male partner will produce a semen sample, which is first “washed” by the embryologist to isolate the best sperm. The sperm is combined with the eggs for potential fertilisation to make an embryo and is monitored in a lab.
Phase 3: The woman undergoing IFV has an embryo transferred to her uterus 3-5 days after egg retrieval and fertilisation.
The ethics of implanting embryos
“Even if a couple undergoing IVF have 10 embryos, we only transfer between one to three to the patient, depending on their preference. The remaining seven can be frozen for future use if they’d like to have another baby later,” says Dr Moodley.
Before an embryo transfer can take place, the individual or couple must sign a consent form that addresses the ethical considerations involved in IVF. This includes important questions, such as what should happen to the embryos if the couple separates or if one partner passes away.
“This consent is vital because we know that circumstances can vary,” says Dr Moodley. “For example, if a couple froze their embryos, the woman could still choose to have a baby even after her partner’s death, as long as this was agreed upon in the contract.”
Success rates of frozen embryos
Eggs, sperm and embryos can be frozen and stored in a laboratory for a maximum of 10 years, says Stacey Wilson, an embryologist at Mediclinic Pietermaritzburg. “But that 10-year cap comes with an asterisk,” she adds. “If a patient stores her eggs at age 40, we advise that she doesn’t wait the full 10 years for transfer but does so by the time she is 45”.
Gynaecologists and embryologists can never guarantee that when an egg is thawed and rehydrated for fertilisation (called vitrification), its quality will be the same as when it was frozen.
Dr Moodley explains that a woman’s age at the time of egg retrieval plays a key role in both egg quality and the overall success of IVF. Generally, the younger a woman is when her eggs are frozen, the higher the chances of a successful outcome later on. Women in their 20s and early 30s also tend to produce more eggs than those over the age of 35.
Wilson adds that the quality of the male sperm is also critical. If there are male infertility issues and the sperm quality is low, intracytoplasmic sperm injection (ICSI) may be required to help fertilise the eggs, she says. This involves injecting a single sperm directly into the centre of an egg – known as the cytoplasm.
Counselling during the IVF process
Dr Moodley says counselling before and during the IVF process < https://www.mediclinic.co.za/en/infohub-corporate/family-life/pregnancy/is-egg-freezing-for-you-.html> is essential for many reasons, one of which is to help patients understand the timeline involved. “It’s important to clear up the misconception that frozen eggs or embryos guarantee unlimited time to have a baby,” she explains. “There are still biological and practical limits, and patients need to be aware of these from the start.
“The age of the parents is also discussed. These are also our responsibilities as doctors as we don’t want to create a generation of orphans just because technology has advanced so much.”
