Semen samples that arrive at the laboratory for assisted reproduction treatments must be processed using sperm capacitation techniques. The aim is to select spermatozoa with the highest fertilizing potential, meaning those with the best functional characteristics for fertilization.
In practice, this process is a key step in the laboratory, as it allows the elimination of lower-quality sperm and ensures that only those with the highest likelihood of success are used. This approach is aligned with the principles described in the WHO Laboratory Manual for the Examination and Processing of Human Semen (WHO, 2021), which establishes the basic criteria for semen processing in the laboratory.
According to IVF-Life Group’s Laboratory Director, Dr. Llanos Medrano, this procedure is essential because it “reproduces in the laboratory part of the natural selection process that occurs in the female reproductive tract.”
Sperm capacitation is a laboratory technique designed to prepare a semen sample by selecting the most competent sperm for fertilization.
Naturally, this process occurs in the female reproductive tract after ejaculation. During their journey toward the oocyte, sperm undergo physiological changes that enable them to acquire fertilizing capacity. In the laboratory, this process is partially replicated, as described in the clinical guidelines of the European Society of Human Reproduction and Embryology (ESHRE, 2023) on male factor management.
The objective is to separate sperm with the best motility and morphology from other semen components such as dead cells, cellular debris, leukocytes, or poorly motile sperm.
The purpose of this technique is to improve the functional quality of the sample used in assisted reproduction treatment. Specifically, it allows:
Sperm capacitation is particularly important in intrauterine insemination, as sperm are placed directly into the uterus. It is also an essential step in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), where the sample must be optimized before laboratory fertilization.

In clinical practice, sperm capacitation is performed in all treatments using ejaculated semen. However, it is especially important in certain scenarios. It is commonly used in the following cases:
It is also essential for cryopreserved samples, as after thawing the sample must be washed and only viable sperm selected.
These indications are consistent with recommendations from the American Society for Reproductive Medicine (ASRM), which defines semen evaluation and optimization as part of standard management of the male factor in assisted reproduction.
One of the most important post-capacitation parameters in the seminogram is the REM (Recovered Motile Sperm count). This indicator reflects how many motile sperm have been recovered after sample processing.
In addition to REM, other laboratory parameters are also assessed, such as progressive motility, sperm concentration, and viability.
Depending on the treatment, approximate REM values may vary:
| Assisted reproduction technique | REM after capacitation | Interpretación |
| Intrauterine insemination (IUI) | ≥ 5 millon | Good overall prognosis |
| Conventional IVF | Variable | Depends on clinical case |
| ICSI | Very low viable number | Individual sperm selection |
These values must always be interpreted within the clinical context of each patient and may vary depending on the laboratory.
There are different techniques for sperm capacitation, and the choice depends on the initial characteristics of the sample and the treatment goal.
This is one of the most commonly used techniques in sperm selection techniques when the semen sample has relatively normal parameters. It consists of removing the seminal plasma and placing sperm in a culture medium. The most motile sperm swim upward into the upper layer, allowing recovery of an enriched fraction of functional sperm.
This technique is frequently used when the sample is more complex, such as when leukocytes, red blood cells, or abundant cellular debris are present. The sample is centrifuged through layers of different densities, separating the most viable sperm from the rest of the components.
In specific cases, especially when there are severe semen abnormalities or repeated fertilization failure, additional sperm selection techniques may be used, such as:
These methods allow more precise selection based on functional sperm characteristics.