Causes of infertility and sterility

In 30% of all cases, the cause is in the female partner. In another 30% of all cases, the cause is in the male partner. In 30% of all cases, the cause is in both partners: combined sterility. In 10% of all cases, the cause is unknown: unexplained infertil

Causas de infertilidad y esterilidad - Instituto Bernabeu
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Causes of infertility and sterility in women

Diseases of the ovary and the uterus:

  • Endometriosis is the reason behind many sterility issues. As well as generally causing pelvic and menstrual pain, it is estimated that around 40% of women faced with difficulties getting pregnant have endometriosis.
  • Polycystic ovary syndrome causes infrequent periods or a total absence of them and is the most common cause of anovulation (an absence of ovulation).
  • Premature menopause and ovarian failure. The menopause is premature when it occurs before 40 years of age. It must be kept in mind that a woman is no longer fertile around six years prior to the menopause.
  • Hereditary causes: due to chromosome or genetic abnormalities.
  • Structural abnormalities in the uterus: these can affect the cervix or the uterine corpus.  Anomalies can be anatomical (septate uterus, T-shaped uterus, etc.) or pathologies that generate embryo implantation issues or issues with how the pregnancy progresses: polyps, endometritis, Asherman's syndrome - synechiae or adherences of the walls of the uterine cavity - or myomas, a benign tumour that generates anatomical distortion and makes getting pregnant complicated (this is one of the most common pathologies but does not necessarily cause fertility issues).
  • Fallopian tube factor: in vivo fertilisation takes place inside the fallopian tubes. Any abnormality in the tubes can affect or impede conception: hydrosalpinx, tubal occlusion or salpingitis.

Age, socio-economic, cultural and other environmental factors:

  • Over the last few years, age has become the most common of these causes of infertility. Difficulties getting pregnant increase from 35 years of age. The optimum fertile period is around 23 years of age when only 5% of women have issues getting pregnant. From that point onwards, there is a progressive decline up to the point when a woman reaches 37 years of age. 30% of women face reproduction issues at this age because ovarian reserve decreases, there are fewer eggs and they are of an inferior quality. At the same time, the number of pregnancy losses and malformations in the foetus increase. Unhealthy living and poor eating habits, as well as exposure to toxic substances such as alcohol, tobacco and other contaminants, also have a negative impact on fertility.

Causes of infertility and sterility in men

The male factor is difficult to evaluate because sperm analyses do not always indicate if there is a problem or not.

Unfortunately, clinical examinations, ultrasounds and analyses rarely indicate the reason for the problem and, as such, medical or surgical treatment is infrequent.

On the contrary to women, in which is the issue can more commonly be detected, most male fertility issues, other than those caused by infections, are unexplained.

  • Lifestyle and environmental factors such as smoking, alcohol and drugs, poor eating habits, exposure to increases in testicular temperature (for example, in professions where the worker spends many hours sitting down) and exposure to toxins are factors that compromise semen quality.
  • Obesity and stress. Recent research carried out in Sweden covering stress markers in saliva demonstrated that patients who are stressed have a greater number of reproduction issues.
  • Of particular relevance amongst diseases affecting the testes are testicular infection or orchitis. Also, parotitis o mumps associated with male infertility when it happens during adolescence.
  • Congenital disorders and chryptorchidism (undescended testicles). The later they are detected, the more complicated having children becomes.
  • Chromosomal causes and, in particular, Klinefelter syndrome. With this condition, boys are born with a different chromosomal make-up, generating an absence of spermatozoa production or minimum generation of sperm that ceases at an early age. If it is detected in time, semen can be frozen.
  • Genetic causes: cystic fibrosis. In such cases, the vas deferens connecting the testicle and prostate is not formed. However, nowadays, spermatozoa can be extracted by means of a testicular puncture. Other causes include Y chromosome microdeletion, a depletion of chromosome material that impedes or severely decreases spermatozoa production. The abnormalities need to be evaluated from a genetic point of view because any male offspring would inherit the same issue as the father.

Combined causes of infertility and sterility

A person can often have a subfertility issue that may be helped or made worse depending on their partner's circumstances. For example, for a woman who ovulates sporadically, the quality of her partner's ejaculate and the frequency of love-making can worsen or improve her prognosis.

Unexplained causes of infertility and sterility

Unfortunately, a basic fertility analysis cannot provide an answer for all causes of infertility and some remain unexplained.

As a result, the final diagnosis is often determined following in vitro fertilisation when it is possible to get an idea of the ability to fertilise and the quality of the couple's embryos.

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