IVM consists in collecting immature egg cells from an ovary during a non-stimulated cycle or a cycle stimulated with low doses of medications which induce follicular growth.
Immature egg cells (oocytes) are retrieved from small antral follicles prior to spontaneous ovulation; they are left to mature in laboratory settings outside a woman’s body; then the fertilization is carried out using the classic technique or ICSI, and at the end of the process embryo transfer is performed.
The stage of hormonal ovarian stimulation may be skipped totally or be limited to only 3 to 6 days of drug administration, which means that it is definitely shorter than the typical stimulation for the standard in vitro fertilization program.
After collection, egg cells mature for 24 to 52 hours on a special culture media (with added small amount of hormones, growth factor, steroids, and proteins) until they reach the stage of metaphase of the second meiotic division (MII) – that is the stage of the egg cell, which is released during ovulation and collected in the standard IVF program. Egg cells maturing within 30 hours seem to be more capable of further development than those which mature later.
The egg cell collection does not differ much from the same procedure in the standard IVF program. In the case of IVM, fluid is collected from follicles with smaller dimensions, i.e. with the diameter of 4-12 mm (as a standard, the size of these follicles is 16-26 mm), and the number of follicles is usually higher. Due to the smaller size and higher number of follicles as well as the smaller and more mobile ovary (since it is not stimulated or only minimally stimulated), the procedure lasts a bit longer than the standard “pick-up” procedure.
The risk of bleeding associated with ovum pick-up in the IVM program may be higher than in the standard program.
In the IVM procedure, it is important to prepare the uterus properly for implantation within only few days between oocyte collection and embryo transfer. Immature oocytes are usually collected before the dominant follicle develops, therefore, until egg cells are collected, endometrium is subjected to the effects of relatively low levels of estradiol. In the result, there is certain asynchronization between the stage of uterine preparation and the stage of embryos ready for implantation. For these reasons, the appropriate preparation of the uterus is extremely important, especially if we take into account the fact that in the IVM cycle, there is no LH surge at the time of oocyte collection.
The typical procedure involves the administration of appropriate doses of estradiol from the time of pick-up and of progesterone 48 hours later until the time of ICSI or insemination. If a pregnancy is achieved, continuation of hormone supplementation is important.
The IVM procedure is simple, the problem of the lack of effects of stimulation and the risk of ovarian hyperstimulation practically do not exist, and the costs of its performance are lower since no medications or only their small amount is needed for ovarian stimulation.
Indications for the procedure
The main indication for the application of the IVM procedure is polycystic ovary syndrome. Important criterion for considering the IVM application is not only the diagnosis of PCO but the number of antral follicles which determinates the number of collected immature oocytes. The highest success rate with IVM is observed in women under 35 years of age who have not less than 10 antral follicles. When the number of follicles is less than 5 in each ovary in the basic ultrasound exam –
IVM is not the procedure of first choice
Indications for IVM procedure may be extended by other indications, including the prevention of side effects of gonadotropin treatment and the prevention of the hyperstimulation syndrome.
IVM can be taken into account when the applied procedure has to be less expensive, in order to simplify the stimulation, treatment in young women with normally poor response to stimulation, preservation of reproductive potential in patients subjected to radio- or chemotherapy, preservation of fertility for a later time (by oocyte or embryo freezing), if the cause of the infertility of the treated couple is male factor (the woman does not need drugs for stimulations), if poor quality embryos were obtained in previous cycles, or when previous IVF cycles failed.
Effectiveness of IVM
The rate of pregnancies achieved after the treatment using the IVM technique compared to the standard in vitro fertilization program is nevertheless lower and amounts to 8.5% per procedure (Hum. Reprod., Vol.25, No.8 pp. 1851–1862, 2010). There are still studies being conducted on the impact of IVM on the health of children conceived with the use of this method. Until now, several hundred pregnancies and children have been analyzed, and the increased rate of congenital defects as compared to the standard IVF has not been demonstrated. Nevertheless, it is difficult to assess clearly the safety of this treatment due to the low number of procedures performed globally.