Special procedures

Sperm microinjection or ICSI

In vitro fertilization (IVF) is an assisted reproductive technique in which eggs are fertilized by sperm in a laboratory and the embryos are deposited in the uterus of the patient. In conventional IVF, the oocytes1 are placed in a culture plate where 100,000 sperm2 are added for each oocyte and it is kept at 37ºC, in humidity and gassing conditions suitable for fertilization to take place.

In some cases, the specialist doctor indicates the use of the sperm microinjection technique or ICSI. This technique is used in cases where there is a male factor with significant alterations in the semen, in cases of not achieving fertilization with the conventional IVF technique in previous cycles or in cases of valuable semen samples (frozen samples of vasectomized men, treated with chemotherapy or radiation therapy).

A few hours after obtaining the oocytes, the embryologist observes them in detail in order to select those that are mature. Sperm microinjection consists of the introduction of a sperm, by means of a micropipette, into each of the mature oocytes. Thus, fertilization rates of approximately 70% are achieved. The quality of the embryos obtained is comparable to that obtained by conventional IVF, with the same probability of implanting in the uterus and developing correctly. The subsequent follow-up of pregnancy and delivery should be done on a regular basis, without requiring more controls than with a spontaneous pregnancy.

IMSI

The acronym IMSI stands for morphologically selected intracytoplasmic sperm injection. It is a very new technique that allows the selection of the sperm to be used in intracytoplasmic injection since instead of viewing it at 400 magnification as in conventional ICSI, it is done at about 6500. This allows biologists to rule out sperm that have minimal alterations .

This technique is indicated in cases of repeated implantation failures after conventional ICSI, severe teratozoospermias, patients in whom the seminogrma shows alterations in the study of DNA fragmentation or long-term sterility of unknown origin.

Embryo cryopreservation

If the quality of the remaining embryos of an IVF cycle allows it, they can be frozen for later use. The freezing of these embryos is a risk for them and to protect them as much as possible, the procedure should be done in a very studied way.

Currently there are two techniques to freeze embryos, slow freezing that consists of completely dehydrating the embryonic cells, incorporating cryoprotectants inside to avoid the formation of ice that would destroy the cells and then cooling the embryos slowly until reaching -196ºC, at which time which are stored in liquid nitrogen. For their thawing, the reverse is done as in the freezing process, the cryoprotectant must be removed and the embryo hydrated well. After this process, 65-70% of the embryos are viable.

The pregnancy rate in in vitro fertilization with frozen embryos is lower than that of fresh embryos since they can lose the capacity to implant and is around 35%.

The second technique is vitrification, which consists of flash freezing of embryos, which is being used lately and seems to have a higher pregnancy rate than traditional freezing. This vitrification technique avoids the formation of ice crystals, minimizing the risk of damaging cellular structures.

Both with one technique and the other, the embryos can be kept frozen until the couple decides the fate of these embryos, which can be their use in subsequent cycles, donation to other couples or donate them for research purposes.

To carry out an IVF cycle with frozen embryos, a visit should be made in which the treatment to be carried out will be indicated, to achieve optimal preparation of the endometrium, a previous treatment with estrogens must be carried out, which can be orally or in transdermal patches .

After the transfer, a treatment with progesterone in vaginal tablets is usually carried out for 15 days. Pregnancies achieved with thawed embryos have the same normality rates as those born by natural methods.

Assisted hatching

It is a complementary technique in in vitro fertilization to facilitate the exit of the embryo from the layer that covers it, the so-called zona pellucida, and thus favor implantation. The zona pellucida naturally thins progressively until the embryo emerges and implants itself in the woman's womb. In some cases, assisted hatching is performed, which consists of thinning or making a small hole in the zona pellucida.

For this purpose an enzymatic solution or a laser coupled to the microscope is used.

It is a technique used basically in embryos in which a thicker zona pellucida is observed, in some elderly patients or in couples with previous implantation failures. Assisted hatching increases the success rate of IVF patients found in the above cases but does not increase the pregnancy rate if performed on all IVF patients.

In vitro maturation

Immature oocytes can be punctured-aspirated to later mature them in the laboratory and then be fertilized and transferred in an IVF cycle. With this technique, women do not require ovulation induction treatment, so it is indicated in patients at risk (or a history) of developing ovarian hyperstimulation syndrome, or in patients who do not respond to ovulation induction treatment.

The downside of this technique is the lower success rate (about 20-25%) and the higher abortion rate (about 30%) than with conventional IVF.