How to select the best sperm in a fertility treatment?

best sperm selection

As an expert and director of the In Vitro Fertilisation (IVF) laboratory at Vida Fertility Madrid, Dr. Álvaro Martinez, explains one of the most crucial aspects in fertility treatments: selection of the best sperm, especially when dealing with the male factor in infertility.

Selection of the best sperm: What does a sperm look like and what does it do?

The spermatozoon – aka sperm – is the male gamete, whose main function is to fertilise the egg. The morphology of the spermatozoon consists of three parts: head, neck and tail. The tail, which allows it to travel to the egg; the neck, which houses the mitochondria that act as a motor and provide energy for the movement of the tail; and the head, which houses the genetic information.

Genetically, the sperm is a haploid cell, which means that it contains 23 chromosomes, half of the genetic material needed to form a zygote. In addition, the sperm cell determines the sex of the baby, depending on whether it carries the X (female) or Y (male) chromosome.

sperm selection

Sperm are formed in the testis through a process of cell divisions called meiosis, which reduces the genetic content. After passing through different ducts, they are stored in the epididymis until they are released during ejaculation, travelling towards the fallopian tubes to meet the egg.

Selection of the best sperm: What alterations can spermatozoa have?

There are various irregularities in the sperm that can complicate the process of conception in a natural way. These irregularities can be detectable alterations in the sperm count such as concentration, motility or morphology; or genetic alterations such as sperm DNA fragmentation.

What is Oligozoospermia?

Oligozoospermia is a seminal diagnosis that refers to a low concentration of spermatozoa in the sample. It is a characteristic that can vary either due to impaired sperm production, abstinence, loss of the sample during collection, etc.

Asthenozoospermia: causes and how to solve it

Asthenozoospermia is the altered diagnosis of sperm motility in the semen analysis. Sperm motility can be altered by abstinence, temperature or pathologies such as Kartagener’s Syndrome.

Sperm alteration due to Teratozoospermia

The diagnosis of teratozoospermia corresponds to an altered morphology of the spermatozoa, where the head, the neck, the tail or several parts at the same time may be affected.


DNA fragmentation

The sperm DNA is condensed to form the nucleus inside the head. Various external and internal factors can lead to the breakage or fragmentation of one or both DNA strands, which can affect the success of the pregnancy.

The importance of selection of the best sperm

Sperm selection is fundamental to maximise the chances of success in fertility treatment. In the laboratory, we use advanced technologies and meticulous techniques for sperm diagnosis and selection.

In addition to the parameters analysed in the semen analysis, it is possible to evaluate the integrity of sperm DNA. This diagnosis makes it possible to carry out an exhaustive analysis of the male factor, individualising the case and promoting the best sperm selection technique.

How to select the best sperm

Sperm Selection Techniques: how to select the best sperm

Not all sperm are the same, and choosing the most suitable sperm significantly increases the chances of success. At Vida Fertility, we are committed to providing our patients with the best care and the most advanced technology for sperm selection:

  • Sperm capacitation: This technique is used to select those sperm with the best motility. The spermatozoa are placed in a special medium, and those with better motility, which are able to move and be located in a determined fraction, are selected.
  • Density gradient: This technique involves separating the spermatozoa into different layers using a medium with different densities. The semen sample is organised according to cell density, with the less motile sperm being trapped in the corresponding layers. Spermatozoa with good motility will be able to move to the bottom of the medium, which facilitates their selection.
  • The Selection of Morphologically Normal Sperm: The morphology of a spermatozoon is a selection criterion during microinjection (ICSI). Using high resolution microscopes, it is easier to identify and select spermatozoa with optimal morphology.
  • Selection of Spermatozoa with Intact DNA: DNA integrity is important for the success of assisted reproduction treatments. A diagnosis of sperm DNA fragmentation/integrity allows treatments to be carried out with supplementation and healthy habits, and also to be able to choose the best sperm selection technique.
    • Microfluidics (Fertilechipe/Zymot): it is a device based on microfluidic physics that facilitates the selection of spermatozoa with higher motility and reduced DNA chain fragmentation. This selection technique improves embryo morphology and reduces implantation failures or miscarriages.
    • Sperm Slow: This method consists of a dense culture medium through which spermatozoa with better motility and DNA integrity will be able to move. Sperm slow improves the fertilisation rate, embryo quality and implantation rates.

The best fertility treatments when male infertility is present

Male infertility can determine the type of treatment to be carried out, because, depending on the cause and penetrance of the infertility, one treatment or another will be chosen.

According to Dr. Alvaro Martinez these are the most common options:

  • Intracytoplasmic Sperm Injection (ICSI): This technique is commonly used in cases of male infertility with medium to severe involvement, being the recommended methodology in cases of testicular biopsy or testicular aspirate. ICSI or microinjection involves mechanically introducing a selected sperm into an egg.
  • Sperm Donation: In cases where seminal quality is very low or there is an absence of sperm (azoospermia), resorting to a sperm donation bank may be an alternative.

How are sperm donors selected?

In Spain, the process of becoming a sperm donor is governed by specific legal regulations.

These requirements are essential to ensure the quality and effectiveness of the sperm and to avoid the transmission of genetic or contagious diseases.

Criteria for Sperm Donor Selection

  • Age 18 to 35 years.
  • Mental and physical health: Must be excellent, both physically and mentally.
  • Medical tests: Include blood tests and genetic tests to rule out hereditary or contagious diseases.
  • Psychological Evaluation: Necessary to confirm understanding and commitment to the donation process.
  • Anonymity and Legal Compliance: Donations are made anonymously, in compliance with Spanish confidentiality laws.
  • Commitment to the Process: Availability for regular visits to the clinic during the donation period is required.

When to see a fertility specialist?

If you have been trying to conceive for more than a year (or six months if you are over 35) without results, it would be advisable to consult a fertility expert. Selecting the right sperm is an essential part of any fertility treatment.

At Vida Fertility, we apply these advanced and personalised techniques to ensure that our patients have the best chance of success on their journey to parenthood. Always providing the best care and support to our patients.

If you would like more information or have any questions, please do not hesitate to contact us. We are here to help you achieve your dream of having a baby.

24 Nov: Fertile Chip: Optimizing Success in Assisted Reproduction Treatments

FertileChip, an innovative device that facilitates the sperm selection with enhanced mobility and reduced DNA fragmentation.

19 May: Infertility tests: Do you know what the most frequent ones are?

Infertility tests allow us to detect the causes that are preventing you from achieving your dream of starting a family.

03 Apr: Male infertility and semen pathologies

Male infertility can be due to various causes such as heavy medication, exposure to high temperatures, smoking, excessive alcohol consumption, STIs or sperm abnormalities

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