Unlike insemination, this technique consists of obtaining the ova, fertilizing them in the laboratory and then placing them into the uterus. It comprises the following steps:
1. Ovarian stimulation:
Drugs are usually used to stimulate a greater production of oocytes (between 10 and 12 eggs, i.e. superovulation) to increase the possibility of success. This stage is controlled using vaginal ultrasounds and tests to determine the level of blood estradiol. When the follicles are thought to be mature (a diameter of between 16-18 mm), the extraction of the eggs is programmed. If an excessive number of follicles are observed on the scan, it may be appropriate to cancel the stimulation due to the risk of developing what is known as ovarian hyperstimulation syndrome, characterized by an accumulation of liquid in the abdomen, abdominal pain or discomfort, a considerable increase in the size of the ovaries and haemoconcentration, etc., which may ultimately require hospital treatment.
2. Obtaining the eggs:
Once the follicles have matured, the eggs are aspirated from them. This is carried out via ultrasound-guided ovarian puncture in the operating theatre under mild sedation. The operation usually takes around 15 minutes and the patient normally goes home two hours later. The follicular liquid is handed to the laboratory where the egg cells are identified under a microscope, and their quality and maturity are assessed.
3. The fertilisation of the ova and the embryo culture:
Egg and sperm cells are brought together on the same day as the retrieval, which means that a sample of semen must be provided by the man. Depending on the causes of the sterility, either a number of egg and sperms are placed together on a Petri dish, or an intra-cytoplasmic sperm injection (ICSI) is performed, which consists of inserting a spermatozoon into each ovum under a microscope. This technique, which practically guarantees the union between the ovum and the spermatozoon, an essential step in achieving the pregnancy, is used in most IVF treatments.
After about 16-20 hours, the number of fertilized oocytes can be determined under a microscope. In average, 7 out of 10 inseminated oocytes are fertilized. After a few more hours in culture, the fertilized oocytes start to divide and the embryo development starts. Once divided, embryo morphology is evaluated to ascertain the number of viable embryos, and so set a date for the embryo transfer.
4. Embryo transfer:
Unlike the retrieval, the process for returning the embryos to the uterus does not require anaesthetics and it is usually a fast and simple procedure. Under ultrasound guidance, to make sure that they are put in the right place, the embryos are placed into the uterus through the cervix by means of a plastic catheter.
Once the number of viable embryos is known, a decision is taken as to how many will be transferred, while the rest are cryo-preserved and stored in the embryo bank for subsequent attempts. The number of embryos to be transferred is determined on the basis of various parameters such as embryo quality, characteristics and age of the patient, previous pregnancy attempts via IVF, etc. Usually, 1 or 2 embryos are transferred –the transfer of 3 embryos (the maximum allowed by law) is exceptional.