The process of culturing embryos directly relates to the artificial insemination procedure. Today, the infertility of one of the partners is no longer the final verdict on the possibility of having children, because, thanks to medical advances, the 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 in pairs, 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 use
In vitro fertilization implies that conception itself does not occur in the female body, but in the laboratory. If, due to certain circumstances, a woman cannot become pregnant, and the elimination of these factors is difficult or impossible, IVF gives high chances to bear and give birth to a baby even with some health problems in a man or woman.
IVF is prescribed in cases when the patient is diagnosed with obstruction of the fallopian tubes, or if they have been removed, if the man has a low amount or low sperm activity, or if 2-4 cycles of stimulation of ovulation or intrauterine insemination were previously performed, but they were unsuccessful.
If a woman has a small number of eggs, this factor may be an indication for IVF using donor eggs.
IVF is also effective in endometriosis, a disease that causes uncontrolled proliferation of the uterine mucosa.
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 to develop an IVF protocol - this term refers to the regimen of administering hormonal drugs designed to stimulate the ovaries to produce eggs. Drugs can be administered orally, intravenously, intramuscularly, necessarily in a strictly defined order and under the supervision of a doctor.
As soon as the eggs mature, they are removed surgically and fertilized by male sperm in the laboratory.
The next step is the cultivation of embryos in a sterile incubator medium. On average, this period takes from 2 to 6 days. All this time, fertilized eggs are under the supervision of reproductive specialists.
Upon reaching the desired stage of development by the embryos, they are transferred to the uterine cavity of the woman. Usually two embryos are implanted in the uterus, the second is transferred there some time after the first to increase the likelihood of pregnancy.
Next, doctors go 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 embryo cultivation
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 is that cell development does not occur in vivo, but in an artificially created environment. The composition and quality of such a medium are identical to the contents of the fallopian tubes, the state of the walls and uterine cavity.
How does the preparation for egg collection (puncture) take place
The cultivation of embryos implies the need for physical removal of the egg from the woman’s ovary. Such a procedure requires mandatory preparation, the rules of which a woman begins to observe in advance. For five days you should avoid sexual intercourse, abandon the use of alcohol, fried, smoked, fatty foods. It is forbidden to visit the bathhouse, sauna, take hot baths.
On the eve of the procedure should be:
- refuse dinner (eating is allowed 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 best not to wear them during surgery.
The date of the procedure should be related to the time of natural ovulation.
Egg puncture technique
In fact, the procedure is not particularly different from 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 nozzle - a puncture device.
The patient can be immersed in a state of drug sleep, or local anesthesia, as the procedure itself causes some discomfort and pain.
After examining the nearby organs, the doctor examines the condition, size and location of the ovaries immediately before the puncture.
Further, the doctor, using the guide line of the sensor, determines the accuracy of the puncture needle getting into the follicle. After that, the needle itself extends from the device, which punctures the wall of the vagina and follicles.
The device absorbs the contents of the follicle in the same way as blood is taken from a vein - air pressure. The aspiration needle is drawn into the device, after which it is removed from the vagina. The contents 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 lasts 10-15 minutes. If a woman has a large number of matured eggs, the puncture procedure can last 40-50 minutes.
In the next two days after surgery, a woman may feel weakness, pulling pains in the lower abdomen, drowsiness. Minor spotting from the vagina is allowed.
The stage of cultivation of embryos during IVF
After taking the eggs, they are fertilized - this usually happens a few hours after the puncture. From the moment the doctor evaluates the onset of fertilization, the start of the cultivation phase is counted. The day of the follicle puncture procedure is considered zero.
In general, the cultivation step 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 existing oocytes, approximately 10-15% are unsuitable for further cultivation, as they are immature or have degenerative forms.
In 16-20 hours after insemination, the stage of presygotes is observed in the eggs: the male and female types of genetic material are already present in the cell, which have not yet merged into a single whole. In this case, fertilization is considered successful.
There are cases when one or an 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 undergo conservation. It is extremely rare that zygotes are transferred to the female body on the first day: first, at this stage the embryo should still be in the fallopian tubes for some time, and not in the uterus, and secondly, doctors prefer to wait for the stage of natural rejection of embryos to begin, as well as manifestations they have any indicators by which the embryo most successful for further pregnancy can be selected.
Second day. In fertilized eggs, they are split into two parts - blastomeres. During this period, doctors can already assess the quality of the embryo by the ratio of the volume of the embryo to the nuclear-free fragments in the cytoplasm. Cells in which the number of nuclear-free elements exceeds the embryo in volume are considered to be a 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 into the female body.
The third day. At this time, the number of fertilized blastomeres approaches 6-8 cells. During the first two days, the development of the embryo was due to the resources accumulated by the egg during its maturation in the ovary. If the cell has chromosomal pathologies, on the third day it stops in development, that is, the so-called process of natural rejection comes into play.
For a long time since the invention of the IVF method, embryo transplantation occurred on that day, since a longer cultivation process was unavailable 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 the intercellular contacts are compacted, and the surface of the embryo is smoothed. The fourth day is also characterized by the onset of the morula stage. In the female body at this time, the fetus passes through the fallopian tubes into the uterine cavity. That is why embryo implantation often occurs at just such a 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 trophectoderm and embryoblast.
Trofectoderm refers to the outer layer of the embryo - it is responsible for its attachment to the uterine epithelium. Embryoblast forms the initial development of the fetal body, and is a collection of cells inside the trophoctodermal 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 components (trophectoderm and embryoplast).
The most effective implantation of the embryo is carried out precisely on the fifth or sixth day of cultivation.
According to statistics, every second embryo of the sixth day is placed in the uterus with a further successful outcome. Thus, it is possible to avoid manifestations of multiple pregnancy and the transfer of a large number of embryos into the uterus to increase the degree of success of the IVF procedure.
Embryo Cryoculture: Conservation Process
In some cases, egg insemination gives 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 undergone the fertilization process, 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 canned embryos is prescribed for 7-10 days from the beginning of the ovulation cycle.
If the cycle is broken, first it is restored through hormonal therapy.
Conducting IVF using frozen cells somewhat reduces the chances of a successful pregnancy.
The success of the laboratory stage of IVF, including the process of cultivation of embryos, depends on the quality of the initial biological material - sperm and eggs, as well as on the experience and qualifications of physicians involved in the cultivation process. Cultivation takes up to 6 days, with the most successful implantation being carried out on the fifth or sixth day of embryo development.