Embryo culture

The process of culturing embryos is directly related to the procedure of artificial insemination. Today, the infertility of one of the partners is no longer the final verdict on the issue of the possibility of having children, since, thanks to the achievements of medicine, procedures for fertilizing eggs in vitro are available, including the method of in vitro fertilization (IVF method).

It is IVF that is considered one of the most effective ways to conceive a child by couples in which, due to the presence of certain pathologies or diseases, a woman cannot conceive or bear a fetus, or a man has reproductive problems. This method is a method of overcoming infertility, but it does not cure it.

General concept of IVF: stages of the procedure, indications for the appointment

In vitro fertilization implies that conception itself does not occur in the female body, but in a laboratory. If, due to certain circumstances, a woman cannot become pregnant, and the elimination of these factors is difficult or impossible, IVF gives a high chance of bearing and giving birth to a baby, even with some health problems in a man or woman.

IVF is prescribed in cases where the patient is diagnosed with obstruction of the fallopian tubes, or if they have been removed, if the man has a low number or low activity of spermatozoa, or if 2-4 cycles of ovulation stimulation or intrauterine insemination were previously carried out, but they were unsuccessful.

If a woman has a low number of eggs, this factor may be an indication for IVF using donor eggs.

IVF is also effective for endometriosis, a disease that causes uncontrolled growth of the uterine lining.

The whole procedure is quite complex and lengthy, it is carried out in several stages, arranged in strict sequence.

Initially, the couple undergoes a general clinical and biochemical examination to detect the presence of indications or contraindications for IVF. The next step is the development of an IVF protocol – this term refers to the regimen for the administration of hormonal drugs designed to stimulate the ovaries to produce eggs. Drugs can be administered orally, intravenously, intramuscularly, always in a strictly defined order and under the supervision of a doctor.

Once the eggs are mature, they are surgically removed and fertilized with male sperm in the laboratory.

The next stage is the cultivation of embryos in a sterile incubator environment. On average, this period takes from 2 to 6 days. All this time, fertilized eggs are under the supervision of reproductive specialists.

When the embryos reach the desired stage of development, they are transferred to the woman’s uterine cavity. Usually, two embryos are implanted into the uterus, the second is transferred there some time after the first, in order to increase the likelihood of pregnancy.

Next, doctors move on to support the luteal phase of the menstrual cycle – the stage when the body produces hormonal preparation of the uterus for pregnancy.

The essence of the process of culturing embryos

The cultivation process is the creation of conditions for the fertilization of the egg, as well as monitoring the development of the embryonic organism from it. The peculiarity of this process lies in the fact that cellular development does not occur in natural conditions, but in an artificially created environment. The composition and quality of such an environment are identical to the contents of the fallopian tubes, the state of the walls and cavity of the uterus.

How is the preparation for the collection (puncture) of eggs

Embryo culture involves the physical removal of an egg from a woman’s ovary. Such a procedure requires mandatory preparation, the rules of which a woman begins to follow in advance. For five days, you should avoid sexual intercourse, refuse to drink alcohol, fried, smoked, fatty foods. It is forbidden to visit the bath, sauna, take hot baths.

On the eve of the procedure, you should:

• refuse dinner (it is allowed to eat no later than 17:30);
• remove varnish or any coating from the nail plates;
• do not drink liquid after 24:00.

In the morning before the puncture, it is forbidden to smoke, eat, drink, chew gum. If a woman wears contact lenses, it is better not to wear them during the operation.

The date of the procedure should correlate with the time of natural ovulation.

Oocyte puncture technique

In fact, the procedure is not particularly different from a transvaginal ultrasound. A special sensor is inserted into the patient’s vagina, which displays an image on the screen of the device. However, unlike ultrasound, the sensor has a special attachment – a device for puncturing.

The patient can be immersed in a state of medical sleep, or local anesthesia can be performed, since the procedure itself causes some discomfort and pain.

After examining nearby organs, the physician examines the condition, size and location of the ovaries immediately before the puncture.

Next, the doctor, using the guide line of the sensor, determines the accuracy of the puncture needle entering the follicle. After that, the needle itself is pulled out of the device, which pierces the vaginal wall and the follicle.

The device sucks the contents of the follicle into itself according to the same principle as blood is taken from a vein – air pressure. The aspiration needle is retracted into the device, after which it is removed from the vagina. The content of the follicle, together with the egg, is determined in a special sterile tube. The procedure is repeated until the desired number of eggs is removed from the follicle.

The whole process usually takes 10-15 minutes. If a woman has a large number of mature eggs, the puncture procedure can continue for 40-50 minutes.

In the next two days after the operation, the woman may feel weakness, pulling pains in the lower abdomen, and drowsiness. Minor spotting from the vagina is allowed.

The stage of embryo cultivation in the process of IVF

After the eggs are collected, they are fertilized – this usually happens a few hours after the puncture. From the moment when the doctor evaluates the fact of the onset of fertilization, the beginning of the cultivation stage is counted. The day of the follicle puncture procedure is considered zero.

In general, the cultivation phase takes up to six days.

First day. The doctor examines the oocytes (eggs that have been fertilized). Most of them already show signs of successful fertilization. However, of all the oocytes present, approximately 10-15% are unsuitable for further cultivation, as they are immature or have degenerative forms.

16-20 hours after insemination, the eggs have a prezygote stage: the cell already contains male and female types of genetic material that have not yet merged into a single whole. In this case, it is considered that fertilization was successful.

There are cases when one egg is fertilized by two or more spermatozoa – such embryos are rejected and do not participate further in the cultivation process. Perhaps the complete absence of the result of insemination, when not a single egg is fertilized.

During this period of time, the fertilized cell can be preserved. It is extremely rare on the first day that the zygote is transferred to the female body: firstly, at this stage, the embryo must still be in the fallopian tubes for some time, and not in the uterus, and secondly, doctors prefer to wait for the onset of the natural culling of embryos, as well as manifestations they have any indicators by which it is possible to select the most successful embryo for further pregnancy.

Second day. In fertilized eggs, they are crushed into two parts – blastomeres. During this period, physicians can already assess the quality of the embryo by the ratio of the volume of the embryo to non-nuclear fragments in the cytoplasm. Cells in which the number of non-nuclear elements exceeds the volume of the embryo itself are considered material with a low potential for implantation.

If on the second day it is possible to select one or two eggs of suitable quality, they can already be implanted in the female body.

Third day. At this time, the number of fertilized blastomeres approaches 6-8 cells. During the first two days, the development of the embryo occurred due to the resources accumulated by the egg during its maturation in the ovary. If a cell has chromosomal pathologies, on the third day it stops developing, that is, the so-called natural rejection process comes into play.

For a long time since the invention of the IVF method, embryo transplantation took place on this very day, since a longer cultivation process was not available due to the imperfection of the laboratory equipment existing at that time. Now this problem is solved by the development of more modern IVF technologies.

Fourth day. The number of blastomeres reaches 16 pieces. During this period, the process of cell compaction begins. It lies in the fact that intercellular contacts are compacted, and the surface of the embryo is smoothed. The fourth day is also characterized by the beginning of the morula stage. In the female body at this time, the embryo passes through the fallopian tubes into the uterine cavity. That is why the implantation of the embryo often occurs at this moment. At the end of the fourth day, a cavity forms in the morula.

Fifth and sixth day. The embryo passes into the blastocyst stage when the volume of the internal cavity of the morula reaches more than 50% of its total volume. The blastocyst consists of the trophectoderm and the embryoblast.

Trophectoderm refers to the outer layer of the embryo – it is responsible for its attachment to the epithelium of the uterus. The embryoblast forms the initial development of the fetal body, and is a collection of cells within the trophectoderm bladder.

At this final stage of the cultivation process, physicians have the opportunity to assess the quality of the blastocyst by the size of its cavity, by the degree of development of its constituent parts (trophectoderm and embryoplast).

The implantation of the embryo is most effective on the fifth or sixth day of cultivation.

According to statistics, every second embryo on the sixth day is placed in the uterus with a further successful outcome. Thus, it is possible to avoid the manifestations of multiple pregnancy and the transfer of a large number of embryos into the uterus to increase the success rate of the IVF procedure.

Cryocultivation of embryos: the conservation process

In some cases, egg insemination produces more than 2-3 successfully fertilized embryos. If their number reaches 8-10 pieces, doctors may recommend freezing them. If the first IVF procedure fails, the couple will already have material for the next attempt.

Eggs that have just gone through the process of fertilization, blastocysts, as well as four- and eight-cell embryos are suitable for freezing.

The process of transferring previously frozen eggs requires some preparation, while puncture and stimulation of the ovaries are excluded. For women with a normal menstrual cycle and ovulation, the transfer of preserved embryos is scheduled for 7-10 days from the start of the ovulation cycle.

If the cycle is broken, it is first restored through hormone therapy.

IVF using frozen cells slightly reduces the chances of a successful pregnancy.

The success of the laboratory stage of IVF, including the process of cultivating embryos, depends on the quality of the initial biological material – spermatozoa and eggs, as well as on the experience and qualifications of the physicians who carry out the culturing process. Cultivation takes up to 6 days, with the most successful implantation carried out precisely on the fifth or sixth day of embryo development.