Sperm Microinjection: discover one of the most used assisted reproduction techniques

Sperm Microinjection (ICSI) is fundamental in assisted reproduction treatments. Its success rate in CREA leaves no room for doubt: 64.7% of the couples in which this technique was carried out, and whose male members were under 40 years of age, achieved a pregnancy (71.4% if they were under 35 years of age). That is why Sperm Microinjection is one of the most demanded and recommended techniques in some cases of female and male infertility.

What is Sperm Microinjection (ICSI)?

It is a technique developed to fertilize eggs in the laboratory. It consists of introducing, through a micro-needle, the sperm into the interior of the oocyte, thus facilitating the fertilization process. Sperm Microinjection is also known as ICSI, Intracytoplasmic Sperm Injection, which translates into English as intracytoplasmic sperm injection.

ICSI: step by step

The process of Sperm Microinjection is performed in the laboratory. The first step is to select a quality spermatozoon that presents the best morphophysiological conditions, a factor especially relevant in cases of altered morphology and severe oligozoospermia (low concentration of spermatozoa in the semen).

An embryo culture is then performed to check the development of the embryo and record its evolution. Three to six days later, the embryo is transferred into the woman’s uterus.

The quality of the egg also influences the results of Sperm Microinjection. ICSI is performed on mature oocytes, when they are at the optimum moment to be fertilized.

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Differences between ICSI and conventional IVF

The difference between Sperm Microinjection and conventional in vitro fertilization is basically the way in which the union of the gametes is performed.

  • In conventional IVF, an egg and a drop of semen containing thousands of sperm are placed in a laboratory dish, waiting for one of them to be able to pass through the protective covers of the egg and fertilize it.
  • In ICSI, fertilization occurs by micromanipulation, that is, by directly introducing the sperm, previously selected, into the egg.

Another difference between ICSI and IVF is the decumulation of the egg, or in other words, the elimination of the cells of the cumulus-crown complex that surrounds it to facilitate the injection of the sperm. In Sperm Microinjection this decumulation is done before the introduction of the spermatozoon, while in conventional in vitro fertilization it is done one day after fertilization.

Broadly speaking, ICSI and IVF are similar techniques, although the latter is slightly closer to the process of natural fertilization since it is the sperm that manages, by itself, to penetrate the egg.

The choice of one technique or the other depends on the specific conditions of each case. To determine this, it is advisable to carry out a study of the couple, taking into account the male factor, since an altered male factor is one of the main indications for ICSI, and if donated gametes are going to be used.

In which cases is Sperm Microinjection recommended?

Although on many occasions the embryologist will opt directly for ICSI to guarantee the entry of the spermatozoa into the egg, the cases in which Sperm Microinjection is especially recommended are:

  • Diagnosis of severe male factor, including problems of low sperm count, motility or altered sperm morphology. Also when it is required to obtain spermatozoa through a testicular biopsy.
  • Fertility problems in women caused by oocyte abnormalities that hinder fertilization, such as the fact that the eggs have thicker pellucid zones than usual.
  • When there have been partial or total failures in previous cycles by conventional IVF.
  • To avoid alteration of the results of a PGD (preimplantation genetic diagnosis), to rule out possible genetic alterations in the embryo. During conventional in vitro fertilization, although it is normally a single sperm that penetrates the interior of the egg, there are many sperm that remain attached to the egg’s shell. When the embryo is incised to obtain a cell and analyze it genetically, they can be dragged along and their genetic load can be confused with that of the embryo.
  • If the spermiogram detects, in the semen, the presence of anti-spermatozoa antibodies.
  • When vitrified eggs are used, whether they are your own or from a donor.
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CREA, male factor experts

Although in many assisted reproduction clinics the treatment of male factor is limited to performing a semen analysis and having the sperm fertilize the egg, using one or the other technique, approximately half of the couples who have fertility problems have poor semen quality. For this reason, at CREA we believe that the male factor is fundamental to understand the causes of infertility in a couple and that it should be treated in exactly the same way as the female factor. Moreover, its diagnosis is simple, as it is limited to tests such as the study of semen quality, the performance of a genital ultrasound and a hormonal and genetic analysis. With all these data, the choice of the appropriate assisted reproduction treatment is much more effective.