Currently, it is well-known, that every month the female body recruits around 20 oocytes to reach their final stage of maturation, just prior to ovulation. Even though only one oocyte will finally reach ovulation, the remaining oocytes are also capable of achieving maturation and fertilization. However, after ovulation, these remaining oocytes will become atretic and will fail to ovulate.
It has been observed, since the mid 20th-century, that human oocytes can resume their final stages of maturation in vitro. The incidence of in vitro oocyte maturation together with their ability to fertilize in vitro set the basis to introduce a new technique in assisted reproduction technology, known as In Vitro Maturation (IVM).
IVM’s major advantage is that it reduces the requirements of fertility hormones. Thus, from a point of view IVM resembles IVF treatment in a natural cycle, adding the advantage of collecting more than one oocytes compared to a natural cycle. The fewer IVF hormones administered, the fewer side-effects during fertility treatment or in the long run.
Specifically, a lower dose of fertility drugs significantly reduces the risk of developing Ovarian Hyperstimulation Syndrome, one of the most serious complications of IVF treatment. Even though severe ovarian hyperstimulation syndrome is a rare complication, there are still women at high risk of developing it, such as women with polycystic ovaries. IVM might seem as a clear choice for fertility treatment for women with polycystic ovarian syndrome, offering high rates of maturation, fertilization and implantation. This strategy also reduces the risk of ovarian hyperstimulation syndrome.
Oocyte collection in cases of IVM is performed in the same manner as in vitro fertilization treatment cycles. Follicular size and endometrial thickness are measured by ultrasound, in order to program egg retrieval around 10 days after the initiation of menstrual bleeding. Egg retrieval is performed under mild sedation and it is painless for the woman. Immature oocytes are collected and cultured in vitro maturation media for 1 – 2 days when their maturation stage is assessed. On the same day, mature oocytes are fertilized in the laboratory. On days 2 or 3 after fertilization, the good quality embryos are transferred back into the woman’s uterus.
More recently, IVM appeared as a realistic option for women wishing to preserve their fertility, prior to chemotherapy when treating malignant diseases. Treatments as chemotherapy or radiotherapy have detrimental effects on ovarian function and often result in ovarian failure and inability of the ovary to produce viable oocytes. IVM allows the collection of many immature oocytes, without hormonal stimulation and within a short time frame. Thus, time is saved and cancer treatment starts as quickly as possible. Immediately after egg collection and IVM, mature oocytes are cryopreserved for future use.
To date, very few children have been born through IVM worldwide. However, IVM children are healthy and show normal development compared to children conceived naturally.
IVM is a very promising technique. In the near future, IVM will offer a therapeutic choice for women wishing to avoid hormone therapy or wishing to preserve their fertility, prior to treatment for malignant diseases that may adversely affect ovarian function.
As with every new assisted reproductive technology, IVM should only be offered to a suitable group of women and only after counseling on the pros and cons of the method.