In vitro Fertilisation (IVF)
What is In vitro FertiliSation?
Once a couple has undergone the complete sterility study, one of the most usual indicated treatments is In vitro Fertilisation (IVF). This assisted reproduction technique consists of achieving the gametes fertilisation (oocytes and spermatozoids) “in vitro”, that is, in the laboratory. Next, the embryos, which are the product of this fertilisation, are transferred into the woman’s uterus.
embrió (4 cel·lules)
embrió (8 cel·lules)
What are the phases of this process?
1. Ovarian stimulation treatment
It is a hormone stimulation treatment to provoke the growth of several follicles at once. When the oocytes which are conained in the follicles mature, they are extracted so as to create embryos to transfer into the uterus.These treatments usually last 12 to 15 days. Generally, they are preceded by a treatment with a hormone preparation, which avoids the interference of the spontaneous functioning of the ovary with the stimulant treatment.
Each treatment is individualized according to the patient and requires controls during the stimulation (echographies and hormone blood tests). We try to simplify this process in order to make it easier so it does not interfere in the couple’s daily life.
When most of the follicles have an optimum size, they are ready to be aspirated. Then, the follicular puncenture is programmed to obtain the ovules within.
2. Follicular puncture and oocytes collection:
The follicles puncture implies a very simple surgical intervention which does not require hospital admission. It is carried out via vaginal and under echographic control.
During the puncture the follicles, which have developed in the stimulation, are aspirated. The fluid obtained is collected in tubes which are taken to the laboratory where the oocytes will be isolated. The oocytes collected are placed on a plate with the appropriate medium within an incubator, which maintains optimum conditions for culture until the time of in vitro fertilisation with or without the aid of intracytoplasmatic spermatozoid injection (ICSI).
3. Preparation of semen sample:
In parallel to the extraction of the oocytes, a semen sample from the partner is required. His presence is not necessary if the use of cryopreserved sperm sample or donor semen has been previously foreseen.
In any of these cases, the sample is prepared in the laboratory to recover the most valid spermatozoid (in general those with the best mobility) which will be used for the oocytes fertilisation.
4. In vitro fertilisation and intracytoplasmatic spermatozoid injection (ICSI):
The oocytes fertilisation in the laboratory may be performed through a standard in vitro technique or by intracytoplasmatic spermatozoid injection.
Standard in vitro fertilization consists in adding a determined quantity of spermatozoids to the culture plate which contains the oocytes. This technique is only used when the semen sample is within the parameters of normality and the origin of the sterility is feminine.
Intracytoplasmatic spermatozoid injection (ICSI) is used when the semen sample is within the limit of normality or is clearly pathologic. It consists in the introduction of a spermatozoid in each of the “mature” oocytes with a micropipette, that is, in the oocytes which are in conditions for being fertilised.
In both cases, around 70 % of the oocytes are fertilised.
5. Observation of the fertilisation:
17 to 20 hours after the above mentioned process - generally the next day- the oocytes are observed to determine whether they have been fertilised and if any of them has to be ruled out due to any abnormality.
The patents are informed of the report of the fertilisation result by telephone and they are given an appointment to complete the information and to perform the embryos transfer -usually within a period of 48 to 72 hours.
6. Embryos transfer:
The embryos transfer consists of placing the selected embryos into the woman’s uterus. After the puncture, a hormone treatment with oral progesterone is begun. If pregnancy is achieved, the treatment has to be maintained during several weeks. On the contrary, it has to be followed until the appearance of the menstruation.
The number of embryos transferred is variable and depends on different factors. The decision is made together and by common agreement between the professionals of the center and the couple. Factors such as the age, causes and length of sterility, previous pregnancies and, specially, the embryo number and quality are considered. The maximum legal limit of embryos that are allowed to be transferred is three.
While the doctor prepares the patient for the process, the biologist places a catheter joining a syringe with a small quantity of culture medium with the selected embryos. With the aid of the ultrasound scanner, the physician introduces another catheter into the uterus. This catheter will be used as a guide to introduce the embryos carefuly in the most appropiate place.
After the transfer, the patient remains resting for approximately 30 minutes. Before leaving, the patient is informed of the protocol to be followed during the following days until the results of the pregnancy test, which are known two weeks after the follicular puncture.
7. Embryo cryopreservation (“freezing”):
Embryo cryopreservation is a technique which allows the preservation of the embryos remaining after an IVF cycle by freezing for posterior use.
This increases the possibilities of success of the cycle in the cases in which gestation has not been achieved after the “fresh” transfer or facilitates another gestation in the case that this has been achieved in the previous embryo transfer. This process represents a simple way for the patient to have another embryo transfer without the need for repeating hormone stimulation and the controls required by a complete IVF cycle. It also allows preservation of the embryos in case of unforeseen contraindications for embryo transfer into the uterus.
Nonetheless, this is a very delicate process in which the embryos must go through different mediums to achieve total dehydratation of the cells. A medium which acts as a cryoprotector during the decrease in temperature is later incorporated and allows the embryo to remain submerged in liquid nitrogen and in a latent situation with no type of activity.
Not all the embryos obtained are valid for cryopreservation. Cryopreservation is only undertaken if the embryo quality demonstrates its viability.
How are cryopreserved embryos thawed and transferred?
When previously frozen embryos are to be transferred, a medication regimen is provided to the patient (estrogen and progesterone pills or patches) to prepare the uterus. At around day 12-14 of the cycle, an echography is carried out so as to evaluate the appropriate date of the transfer. The number of embryos that will be transferred is decided by the couple.
Before the embryos transfer, the thaw process has to be carried out in order to evaluate its viability. Despite the existence of a high variability, around 70 % of the thawed embryos are viable for transfer. This process is opposite to freezing, in the sense that a correct rehydratation of the embryo must be achieved after eliminating the cryoprotector. Thereafter the embryos are left in culture medium until the time of the transfer is performed as previously described. The embryos transfer process is done in the same way as in “fresh” embryos.