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Egg Freezing or Ovarian Tissue Freezing

H welcomed the recent announcement by the Singapore government that social egg freezing is allowed for women aged 21 to 37. Previously, the procedure was only reserved for women with medical conditions, such as cancer, who wanted to preserve their fertility.

H, aged 34, and single, had no plans for marriage for the next few years. “At least I have a backup plan for fertility when I find my Mr. Right,” she said.

Like most women, she was mindful about her ticking biological clock. She knew that biologically, a woman is born with a finite number of eggs, the quality and quantity of which will decline over time.

She also read about another fertility preservation option- ovarian tissue freezing. In this procedure, part of the ovary is taken out of the body, stored and frozen for future use. She wanted to know which option would suit her best.

What is Egg Freezing?

Egg freezing or oocyte cryopreservation (OC), is an assisted reproduction technology that freezes and stores a woman’s unfertilized eggs for conception at a later stage of her life. The patient has to undergo daily injections of hormones to stimulate the growth of eggs in both ovaries. When these eggs reach a mature stage, they are retrieved by needle aspiration through the vagina under ultrasound guidance. The procedure is done under sedation or general anesthesia. The retrieved eggs are examined under microscope to determine their suitability for storage. These eggs are then frozen through a process called vitrification and stored in tanks filled with liquid nitrogen until the woman is ready for conception.

What is Ovarian Tissue Freezing?

Ovarian tissue freezing is also known as ovarian tissue cryopreservation (OTC). Under general anesthesia, part or whole of the ovarian cortex, the egg-producing portion of the ovary is resected through a key-hole (laparoscopy) surgery. The ovarian tissue is dissected into smaller pieces in the laboratory. These are frozen and stored under liquid nitrogen. When the patient is ready for conception, the ovarian tissues are reimplanted back into the patient’s pelvic cavity by laparoscopy. The patient has to wait for a short while for the return of ovarian function of these reimplanted tissues.

Reasons for doing OC or OTC?

There are two main reasons for fertility preservation:

Medical: Women with medical conditions that threaten fertility: Certain medical conditions such as cancer or its treatment, such as chemotherapy or radiotherapy, may damage the growth and development of eggs. Fertility is thus impaired and irreversible sterility may result.

Social: Women who are not ready to have a baby for personal reasons or professional ambitions or the lack of a suitable partner to begin a family with and who would like to start the family at the later stage of life. Marrying late and postponing childbearing are on the rising trend in most developed countries.

Comparison between the 2 options of fertility preservation:


  • Can be done under sedation or general anaesthesia. Invasive surgery is not required.

  • The chances of successful live birth are dependent on the age at the time of cryopreservation and the number of eggs retrieved.

  • Successful pregnancy, live birth and perinatal outcomes have been reported.

  • More than one cycle may be required to retrieve adequate numbers of eggs to improve chances of successful live birth. It is estimated that in order to achieve a 70–80% chance of one live birth, 2 to 3 treatment cycles may be required to harvest between15 to 20 mature eggs.

  • IVF is the only way to achieve pregnancy.

  • Requires daily hormonal stimulation for about 2 weeks. This may disrupt the everyday activities of the patient.

  • Ovarian stimulation increases the risk (albeit minimal) of thrombotic events (blood clots forming in the circulation) and ovarian hyperstimulation syndrome.

  • Ovarian stimulation increases the risk of borderline ovarian tumours or gynaecological malignancy.

  • Ovarian stimulation is associated with short and long-term psychological and/or hormonal side effects.

  • The preserved eggs may not end up being used, due to spontaneous conception, or through choice. Only 3 –12% of women have utilised their eggs.

  • Not suitable for children, adolescents, and young adult cancer patients who require immediate chemotherapy and do not have enough time for ovulation induction.


  • Can only be done under general anaesthesia.

  • 2 surgeries required, one for resection, and the other for re-implantation. There is a slight increased risk of surgery and anaesthesia.

  • Suitable for children, adolescents, and young adult cancer patients who require immediate chemotherapy and do not have enough time for ovulation induction.

  • Successful outcomes have been reported regarding hormonal function, live birth, pregnancy rates and perinatal outcomes.

  • Women can use cryopreserved tissue later in life to improve their hormonal status.

  • Thousands of egg can be preserved at one time, without the need for hormonal stimulation.

  • Long-term surgical risks such as adhesions, could impair the ability to achieve spontaneous pregnancy in future.

  • Spontaneous pregnancy is possible. Based on recent research studies, about 4 out of every 10 females who tried to get pregnant using frozen ovarian tissue were successful. Half of the females got pregnant naturally, and half after IVF.

  • Tissue may not end up being used, due to spontaneous conception, or through choice.

After thinking through the 2 options, H decided to have OTC which was successfully done recently.

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