In vitro fertilization (IVF) is one of the types of assisted reproductive technology (ART) applied in cases where it is not possible to have a baby naturally. In vitro fertilization consists of a combination of medications and surgical procedures to help sperm fertilize an egg and implant the fertilized embryo into your uterus.
After obtaining the egg and sperm, they are combined in the laboratory and developed into an embryo. It is often difficult to understand why IVF treatment has not been successful after implanting healthy-looking embryos into the womb. As with most biological events, pregnancy is a very complex process. Even today, what we don’t know about pregnancy continues to exceed what we know.
However, there are some specific factors we have identified that can occasionally lead to IVF failure.
Causes of IVF failure
The most important variables involved in a successful IVF treatment cycle are a healthy egg, normal, functional sperm, and a uterus that can nurture the baby’s growth. In addition to these problems, there are many other factors that can affect the chances of conceiving with IVF. These include the laboratory environment, the techniques used in the laboratory, and the skills of the specialists who perform egg collection and embryo transfer.
The human egg is a very complex structure. As such, it is subject to damage that could render it dysfunctional. When cells divide, chromosomes (packages of DNA containing your and your partner’s genes) replicate and line up in the middle of the cell. As the cell divides, half of the chromosomes move in one direction and the other half in the opposite direction, resulting in two identical cells. These chromosomes move because they are attached to a structure called the spindle apparatus, which is responsible for chromosome separation necessary for cell division.
As the egg ages, the spindle apparatus becomes prone to breakage. Such a break can cause an abnormal distribution of chromosomes, resulting in a chromosomally abnormal and therefore non-viable embryo. As the woman ages, the egg is damaged due to the presence of free radicals, reactive oxygen species and other metabolic products that occur in the ovary. Many recent studies have shown that between 25% and 40% of all eggs are chromosomally abnormal. Obviously, this number increases as a woman gets older.
While abnormal sperm may seem like a less common factor affecting the success of IVF, they actually play a very important supporting role. Sperm does not just enter the egg and cause fertilization. On the contrary, the fertilization process itself is very complex. In order for the sperm to migrate to the egg, it must be motile; in other words, the tail of the sperm must be able to push the sperm through the female reproductive tract into the egg.
On the surface of a sperm head are specific receptors that bind to specific receptors on an egg’s outer membrane, allowing for sperm/egg interaction. When this happens, enzymes are released from the sperm head that digest a hole in the egg’s outer membranes. The sperm eventually penetrate the egg, where the nucleus of the sperm opens, releasing the sperm DNA. At this point, chromosomes from the sperm and chromosomes from the egg combine to produce a fertilized egg (which is actually a very early embryo). Studies show that the incidence of chromosomal abnormalities in sperm is much higher than in eggs. However, a chromosomally abnormal egg can lead to a chromosomally abnormal pregnancy, while a chromosomally abnormal sperm does not seem to be able to successfully fertilize an egg.
Intracytoplasmic sperm injection (ICSI) is a method developed to introduce sperm into the egg to enable men with very low sperm count, low motility, or very few normal sperm counts to achieve fertilization and pregnancy. Over the past few years, ICSI has gotten to the point where it is now routinely performed in severe cases of male factor, resulting in fertilization rates comparable to those achieved with normal sperm. In addition, data from long-term studies indicate that the incidence of chromosomal abnormalities in children born from IVF cycles using ICSI does not exceed those found in nature.
Embryo Selection Methods
Embryos transferred to the female uterus are selected by the embryologist. Unfortunately, our ability to distinguish chromosomally normal embryos from chromosomally abnormal embryos is severely limited just by looking at their shape. Essentially, embryologists select embryos for transfer based on three basic criteria: cell shape, cell number, and cell division rate. Embryos that develop to at least the 6-cell stage on the third day have a much better prospect of success than embryos with 5 cells or less.
Embryos determine embryo selection based on cell division rate. For example, an embryo that gradually reaches 8-cell stage on day three is much more likely to be successful towards the end of this period than an embryo that delays fertilization and grows rapidly. The healthiest embryos can be selected with artificial intelligence applications used in embryo selection.
IVF Laboratory Factors
The IVF laboratory is a very tightly controlled environment where we try to imitate the formation of embryos consisting of sperm and eggs, as in the female reproductive system. Especially we strictly control the oxygen concentration, carbon dioxide concentration and other factors such as humidity, PH, temperature and light. Even minor changes from what the embryos normally experience can cause the death of the embryos and thus there is no chance of pregnancy from the resulting cycle.
Problems with egg retrieval and embryo transfer
The surgical procedures themselves, egg collection and embryo transfer are crucial to the success of the IVF cycle. Getting fewer eggs than expected, or worse, no eggs at all can have negative consequences. In addition, embryos must be placed in the right place during the embryo transfer process, which is one of the most important steps of the whole cycle.
In vitro fertilization is an assisted reproductive technique that should be specially planned for couples and has a very high success rate today. The dream of becoming a mother and father can be turned into reality by getting support from IVF specialists.