IN VITRO FERTILISATION (IVF)

What does it involve?

In vitro fertilisation (IVF) is an assisted reproduction technique that entails bringing eggs into contact with spermatozoa using laboratory techniques. The aim is to facilitate and achieve fertilisation.

The embryo or embryos obtained from fertilisation are grown in the laboratory and transferred to the uterus to continue their growth and development. Embryos that are not transferred may be frozen whenever they are developing satisfactorily.

This technique is suitable for either or male partners with some kinds of sterility such as:

• Tubal factor infertility
• Severe male factor infertility (alterations in semen)
• Antisperm antibodies
• Recurrent failure of artificial insemination cycles
• Endometriosis
• Ovarian dysfunctions
• Sterility of unknown origin
• Sterility of genetic origin that requires PGD (preimplantation genetic diagnosis)

STAGES OF IVF

Ovarian stimulation

In physiological conditions, a structure known as a follicle that contains an egg grows every month in each of the ovaries alternately. During ovulation, the ovary releases this egg, which is collected by the Fallopian tube, where, if possible, spermatozoa arrive to fertilise it.

Several mature and good-quality eggs are required to increase the effectiveness of IVF and achieve the pregnancy desired. Controlled ovarian stimulation, with hormonal treatment (gonadotropins), should therefore be performed for 9 to 12 days. This will allow for the growth of several follicles and, therefore, the retrieval of different eggs.

The stimulation protocol best suited to each patient is determined by the gynaecologist. During this period, strict personal and ultrasound scans are run to evaluate the number and growth of the follicles and hormone tests are performed.

When ovarian stimulation is deemed satisfactory, an HCG injection is administered. This allows for the final maturation of the eggs. Egg collection is scheduled for the subsequent 36 to 38 hours.

Egg collection. Retrieval and identification of eggs

Egg collection is the recommended procedure for the retrieval of eggs, while aspirating the follicular fluid. After ovarian stimulation and the administration of HCG, most eggs have just matured, separate from the inner wall of the follicle and are released in suspension into the follicular fluid.

Although puncture takes place in the operating theatre and under sedation, it is a simple and painless operation that does not require hospitalisation. It lasts 15-20 minutes and the patient can return home in just a few hours.

During puncture, the doctor accesses the ovaries with a transvaginal ultrasound transducer. The extracted follicular fluids are taken to the embryology laboratory, where they are identified and placed in culture dishes until the time of in vitro fertilisation.

Eggs are not always retrieved from all the follicles. Some may not contain eggs or they may be immature or degenerated and therefore unsuitable for fertilisation. The number of follicles seen on previous days in ultrasounds does not therefore necessarily match the number of eggs retrieved. Neither the number of eggs obtained nor their quality can be accurately determined therefore until the follicular fluids are observed under the laboratory microscope.

Preparation of the semen sample

At the same time as egg collection, the partner should provide the laboratory with a semen sample. According to WHO recommendations, a 2 to 7 day period of abstinence from sexual relations should be observed.

This sample is processed in the laboratory to select the best quality and most motile spermatozoa and to separate them from the other components of the semen: seminal plasma, immotile or low-motility spermatozoa, other cells, etc.

There are different techniques of semen preparation. The technique is tailored in each case to suit the characteristics of the sample. The ultimate objective is to attain the best spermatozoa and prompt the physiological changes (sperm capacitation) necessary to encourage fertilisation of the egg.

When spermatozoa in the ejaculate cannot be retrieved, a testicular biopsy is required to isolate them from the testicular tissue and to be able to use them for IVF.

Insemination of the eggs

Insemination of the oocytes is performed a few hours later using the most suitable technique in each event:

> In vitro fertilisation: the mature oocytes and spermatozoa come into contact and fertilisation occurs spontaneously. This can be done provided that the semen sample is of sufficient quality. Between 40,000 and 80,000 spermatozoa are used per egg.

> Intracytoplasmic sperm injection (ICSI). Micromanipulation techniques are used to introduce a spermatozoon in the cytoplasm of the egg to produce fertilisation. The eggs of the surrounding cells must be released previously. This is done at a magnification of 400.

Specific techniques

 

> Intracytoplasmic morphologically selected sperm injection (IMSI)

This technique is complementary to ICSI. IMSI involves the real-time preliminary selection of spermatozoa that must be microinjected using an inverted microscope with a higher magnification (around 6,000 times) than that commonly used for ICSI.

Specific techniques

 

Evaluation of fertilisation

16 to 20 hours after insemination, the fertilised eggs (zygotes) are identified and evaluated. 2 pronuclei (one female and one male) should be present inside the egg. These pronuclei contain the genetic information of the parents. They are visible for just a few hours.

Eggs that have not been fertilised or that have not been fertilised properly can be ruled out at this point.

Embryo culture

The embryos obtained are left in culture in the laboratory incubator for 2 to 6 days, depending on the case.

During this time, embryologists supervise and evaluate the development of the embryos with a view to selecting those with the greatest implantation capacity for transfer or freezing.

Diverse criteria are used for this evaluation. Morphological aspects of the embryo, in general, and of the cells that form it, in particular, must be considered. The kinetics and speed of division of the embryo are also evaluated.

Standards established by scientific institutions are used as a reference.

Culture conditions

Eggs and embryos are cultured in special dishes, where they are protected and in suspension. These dishes are kept in an incubator in the conditions of temperature, humidity, pressure and air-purity necessary to cover needs and encourage fertilisation and embryo development.

These environmental conditions, whether in the incubator, the laboratory or the culture medium, must be controlled very thoroughly as they may influence the development and viability of embryos.

Remember throughout the process that these culture conditions should be as similar as possible to the natural environment of the Fallopian tubes and the woman’s uterus.

Embryo transfer

Embryo transfer entails depositing the embryos into the uterine cavity. This takes place 2 to 3 days after egg collection, although in some cases may be performed up to the sixth day.

Transfer involves a selection of the embryos with the best prospects of implantation. The number of embryos to be transferred depends on each situation and on their evolution. The current Law of Assisted Human Reproduction Techniques (Law 14/2006) allows a maximum of three embryos to be transferred in each transfer cycle.

Transfer is done using a special catheter and is ultrasound guided. It is a simple and painless process performed in a room adjacent to the laboratory. Although patients may return home in a short while, they should not exert themselves for a few days.

The patient can find out whether or not she is pregnant in a blood test taken 12 to 13 days after transfer.

Freezing of embryos (cryopreservation)

Good quality embryos that are not transferred in the IVF cycle are frozen. This provides embryos that may be used in a subsequent cycle and thus avoids a repeat of ovarian stimulation and puncture.

Embryos are cryopreserved until the couple wish to undergo a new transfer.

Embryos are kept completely safe in the GIROFIV Embryo Bank.

Frozen embryo transfer

This is a much simpler treatment that allows transfer to the patient’s uterus of the embryos that were generated in the IVF cycle and cryopreserved.

On the days prior to transfer, mild hormonal treatment should be initiated to prepare the uterus to receive the embryos.

Embryos are thawed a few hours before embryo transfer.

Some embryos do not withstand the freezing and thawing process even though advances in freezing techniques have increased the survival rate a lot in recent years.

GIROFIV uses vitrification as a first-choice technique to cryopreserve embryos.