Why do sterility problems exist?

Published: 16 March 2017|Last updated: 30 November 2020|

Sterility is the great fear of couples wishing to have children. It is estimated that it affects about 10-15% of couples of childbearing age.

Unlike what we generally think, getting pregnant is not that easy and it is not always enough to have sexual intercourse as the day of ovulation approaches. The reality is that the human species has a low reproductive capacity, with the possibility of pregnancy being only 18 to 35% per month in a couple under the age of 35 and without any infertility factors. Furthermore, from the age of 35 onwards a woman’s fertility decreases considerably, and her chance of getting pregnant per month is around 10% and progressively drops to 5% by the age of 40.

When a couple wants to have a baby and their quest begins to break down, doubts begin to emerge and words like infertility or sterility become ever more present. Before panicking, we recommend that you have a sterility test after 1 year of frequent and unprotected sex, as even under normal conditions it may not be that easy to get pregnant in this period of time.

Now let’s take a closer look at the world of sterility.

It is important, first of all, to be clear about the definition of sterility and to differentiate it from infertility, as they often get confused. According to the Spanish Royal Academy of Language, these words are synonymous, but from a medical point of view it is important to differentiate the concepts, even though both may signal difficulties in conceiving.

Sterility is the inability to conceive after regular sexual intercourse without using contraceptive methods. Therefore, it is not possible to fertilise the egg and start a pregnancy.

Infertility, on the other hand, is the inability to complete a pregnancy satisfactorily, namely, with the birth of a healthy baby. In this case, it is possible that the egg is fertilised and a pregnancy is achieved, but that the gestation does not proceed optimally and the foetus is not born (miscarriage) or is in an inert state. Therefore, sterility is one of the reasons why infertility can occur.

A problem of sterility or infertility is considered to exist when it has not been possible to have a live birth, after one year of unprotected intercourse, in order to have a baby.

Within sterility, a distinction must be drawn between primary and secondary sterility. The former refers to cases in which the couple has never been able to achieve pregnancy, and the latter is that which occurs in those couples who already have children or who have a history of one or several pregnancies, even if these did not end properly.

There are various factors which cause infertility or sterility in women. Most are irreversible, but those involving anatomical alterations can be solved with surgical intervention. It is becoming more and more accepted that the quality of the egg is of critical importance and this is closely linked to the age of the woman. Women of advanced age have eggs with a reduced capacity for fertilisation:

  • Ovarian factors: This includes all those cases where ovulation does not occur. This is usually due to hormonal problems, either the lack of hormones or the excess of some of the regulators of endocrine function: ovarian polycystic syndrome (OPS), anovulation, ovarian failure or premature menopause.
  • Uterine factors: In this case, infertility and not sterility is much more frequent. Fundamentally, it involves alterations to the internal anatomy of the uterus which may be congenital or acquired and can lead to repeated miscarriages. Congenital uterine deformities include partial or total duplication of the uterus and septums. Causes include polyps, myomas, synechia, and endometritis.
  • Tubal factors: This includes all those anomalies of the Fallopian tubes which prevent the sperm from meeting with the egg: absence, impermeability or obstruction of the tubes, and salpingitis.
  • Cervical factors: In this case, the cause is anatomical and/or functional alterations of the neck of the uterus which interfere with the correct migration of the sperm towards the uterus and the Fallopian tubes in their attempt to reach the eggs. This can be due to impermeability of the neck of the uterus (polyps, cysts) or past surgery (conisation).
  • Genetic factors: Chromosome anomalies which cause miscarriages.

Some of the factors affecting male sterility are:

  • Genetic factors: Most of these are associated with sperm anomalies, either directly or indirectly: cystic fibrosis, karyotype anomalies like Klinefelter’s syndrome, translocations,…In most cases of male infertility and low quality sperm, there are no clear causes that can be identified using the diagnostic methods currently available. There is some speculation that perhaps mutations of the Y chromosome could play an important part.
  • Anatomical factors: Ejaculatory duct obstruction can cause sterility since it blocks the exit of the seminal fluid. Some of these anomalies can be of congenital origin (present at birth) or acquired (infections, scars from surgery on the urogenital tract).
  • Environmental factors: Lifestyle can reduce the quantity and quality of the sperm (tobacco, alcohol, and other drugs).
  • Other types of illnesses: There are illnesses that can appear after birth and that can influence male sterility; infection with the parotiditis virus (mumps), hormonal dysfunction…

In some cases, both men and women can be sterile and the couple’s difficulty in conceiving is a result of a combination of these conditions. In other cases, in which the cause could be immunological or genetic, it is possible that both people can be independently fertile but the couple together cannot conceive without assistance.


In around 10% of cases, the basic sterility study does not show any anomalies. In these cases, the abnormalities are probably present but cannot be detected using the methods currently available.


For the prevention of sterility, it is important to take measures such as: avoiding unprotected sex with partners in unstable relationships, to avoid sexually transmitted diseases and therefore future infertility; vaccination against mumps; or keeping to a healthy diet, weight and lifestyle.

We at Eugin work every day to help couples who suffer from this problem and to ensure that they can have children by combating sterility. That is why we have a group of professionals and experts, as well as the most advanced technology in the sector, aimed at knowing the intricacies of sterility and to find the best solutions and alternatives for each case we encounter.

Do you have a query that can’t wait? Ask our experts.

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