What is the difference between IVF and ICSI?

Classic IVF or ICSI? This is a question that many patients and professionals are asking themselves. The truth is that there is no one technique better than another: simply, depending on each situation one or the other will be recommended. For clarification purposes, we will clarify the main similarities and differences between both assisted reproduction methods.

In vitro fertilization techniques

In the first place, we must make it clear that both techniques are in vitro fertilization processes, since in both cases the union between egg and sperm is produced outside the woman's body. Therefore, we could include them in the term IVF. However, only classical IVF is normally understood as IVF.

The steps followed in both methods are the same:

• Ovarian stimulation
• Follicular puncture
• Semen collection
• Union of gametes (eggs and sperm)
• Embryo culture
• Endometrium preparation
• Embryo transfer
• Pregnancy test

Variations between classical IVF and ICSI

The main difference lies in the way the gametes are joined together:

• Conventional or classic IVF: a drop of semen with thousands of sperm is deposited on a laboratory plate where the ovum is in culture, waiting for at least one of them to be able to pass through the protective covers of the ovum and allow the fusion of both genetic endowments. As a result of this fusion, the embryo is obtained.
• ICSI stands for Intracytoplasmic Sperm Injection. This is a micromanipulation technique in which the professional directly introduces the entire spermatozoon into the interior of the ovum, thus allowing fertilization, that is, the union of both genetic loads to give rise to an embryo.

Ways todo the fusion of egg and sperm

Another point of distinction is the purported decumulation of oocytes. In the ICSI process, after the eggs are obtained and before their microinjection, they are decumulated. That means that the cells of the cumulocorona complex that surrounds them are eliminated to facilitate the injection of the spermatozoid.

In the conventional IVF process, decumulation is performed one day after fertilization, during fertilization assessment.

Both techniques move away from the natural process. However, conventional IVF is slightly closer to what occurs naturally, as it is the sperm itself that has to penetrate the egg without human help.

As aforementioned, choosing one or another technique will depend on the characteristics of each situation, the conditions of each couple and the preferences of the fertility clinic.

When is ICSI performed?

Although there are clinics that perform ICSI generically, this technique of sperm microinjection is recommended in the following cases:

• Severe male infertility: some examples are found in males with oligospermia, asthenozoospermia or obstructive azoospermia in which sperm must be obtained by testicular biopsy...
• Oocyte abnormalities: when we are faced with eggs with certain abnormalities that can hinder fertilization such as eggs with pellucid areas (ovarian cover) thicker than normal.
• Women's age: Older maternal age means lower egg quality, and fertilization may therefore be more expensive.
• PGD: when preimplantation genetic analysis of embryos is needed, ICSI is used to avoid altering the results. In classic IVF, many sperm try to pass through the zona pellucida of the egg. Only one of them gets through, but the rest stays attached to the zona pellucida. By making the incision in the embryo to obtain a cell and analyse it genetically, we can drag some of these spermatozoa and confuse their genetic load with that of the embryo.
• Repeated failures of conventional IVF: these failures may be caused by a lack of receptors (in the egg and/or sperm) that allow adhesion or by the presence of antisperm antibodies, among other causes.

Cases in which ICSI is necessary

FAQs from users

What advantages and disadvantages does ICSI have in comparison to IVF?

ICSI, intracytoplasmic sperm injection, was developed in 1988 as a treatment for male infertility, i.e. men with very poor sperm parameters, to treat fertilization failure with IVF.

ICSI is now routinely used in many IVF programmes as the fertilisation rate is higher than with standard fertilisation techniques and pregnancy rates are higher. There is inadequate information about a possible increase in birth defects with ICSI. There appears to be an increased risk of twins with ICSI, especially with blastocyst transfer. This can be as high as 2%.

What technique is being used in Surrogacy? IVF or ICSI?

A surrogacy process is an IVF process with the only difference that the uterus where the transfer takes place is not that of the future mother. Therefore, when it comes to choosing the technique that offers the best guarantees of success, the same premises will be followed as for an own gestation.

It is important to point out that in many cases of surrogacy, PGD is performed and, therefore, the technique most commonly used is ICSI.

Are the results of a classical IVF better than those of the ICSI?

Not necessarily. As we have already mentioned, the results of both techniques depend on each situation, so there is no technique better than the other. Actually, ICSI takes us a step further towards pregnancy. However, this means more manipulation of the gametes, which can be counterproductive in some cases.

Suggested for you

As we have indicated, both conventional IVF and ICSI are in vitro fertilization techniques. Nowadays, it's common to resort to IVF when opting for surrogacy. If you want to know more about IVF in surrogacy, I recommend you consult this article: What is IVF Surrogacy?

We have also talked about the main indications of microinjection, among which we highlight the serious problems of human fertility and genetic analysis of embryos. Here you’ll find more about it:

• Male Sterility
• Preimplantation Genetic Diagnosis