Causes of infertility

Couples presenting with infertility will often want answers to two questions: 
1. Why are we not getting pregnant naturally?
2. Please get us pregnant. 
Early investigations are designed to try to find a cause for people’s infertility, which may be treatable. It is uncommon that there is simply one absolute ‘cause’ for a couple’s infertility frequently there will be combination of male and female factors. This is often different to people’s initial thoughts that infertility is a female issue. Women and men who we talked to sometimes described feeling guilt (or relief) when the ‘cause’ of their infertility was identified.
Sometimes a couple needs fertility treatment because one of them has been sterilised, perhaps in an earlier relationship. Frances conceived with donor sperm because her husband had had a vasectomy. Laura was having IVF because she had been sterilised after her previous relationship had ended.

Multiple Causes
Often a couple’s infertility is caused by a combination of factors. Sandra’s husband had a low sperm count and she had blocked tubes. Carol’s fertility was affected by both her polycystic ovary syndrome (PCOS) and endometriosis. Sally had a blocked tube and fibroids which were thought to affect the chances of any IVF cycle she undertook.
25% of infertility is attributable to unexplained causes (NHS Choices 2017).
In around a quarter of cases couples have investigations that are inconclusive and are told that they have “unexplained infertility”. This can be very hard for individuals, as Catherine explained, “It all takes so long and so many of the tests are inconclusive. And for lots of people like us there’s never any reason found.” It can also cause problems in the clinical relationship between couples with high hopes of finding a solution and their fertility specialists who have to admit that they don’t know the reason for the problem.
Causes of infertility in women
Factors that can contribute to a woman’s infertility may include endometriosis, damaged fallopian tubes, ovulatory problems and conditions affecting the uterus, the woman’s age, Polycystic Ovarian Syndrome (PCOS), gynaecological problems such as a previous ectopic pregnancy and medical conditions (e.g. diabetes). Lifestyle factors (e.g. being overweight or underweight) can also play a part.

Endometriosis can sometimes damage the fallopian tubes or ovaries, causing fertility problems. As it can often take a long time to diagnose, it can be a contributing factor to infertility. However, it's estimated up to 70% of women with mild to moderate endometriosis will eventually be able to get pregnant without treatment (NHS Choices 2015). Susan for example had severe pelvic pain and endometriosis but she was in her forties before her doctors explained to her it was a potential threat to her fertility. 
Blocked Fallopian Tubes
Fallopian tube disorders which include blocked tubes can often cause fertility problems together with other causes. Sandra had a laparoscopy which revealed one of her tubes was blocked.
Ectopic Pregnancy
An ectopic pregnancy, is a complication in pregnancy where the embryo implants outside the uterus, mostly in the fallopian tube. An ectopic pregnancy can affect fertility if a fallopian tube has to be removed. Clara first had unexplained infertility and then two ectopic pregnancies before she conceived her son with IVF. However, many women conceive normally with only one ovary or fallopian tube.
Polycystic Ovarian Syndrome (PCOS) is one of the most common causes of female infertility (NHS choices 2017). PCOS can also cause acne, hairiness (and hair thinning), weight gain and irregular periods. George said that his wife’s period had been up to 52 days late because of her PCOS, “And of course after day 28 she is thinking ‘oh this might be it’”. 
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Causes of infertility in men
A third of cases of infertility are thought to be due to male factor infertility (Human Fertilization and Embryology Authority 2017). Conditions that may result in male infertility include low sperm count, problems with the tubes carrying the sperm, and problems with erection and ejaculation. Lifestyle factors can also have an impact for men, such as smoking, being overweight or having a job that involves contact with chemicals or radiation. (For more information see Human Fertilization and Embryology Authority or Infertility Network UK.)
Michelle and her husband went to a private clinic that pinpointed the problem as poor sperm quality. This was a considerable shock to them both because they had been told before there was no problem with Brian’s sperm count.

Last reviewed July 2017.
Last updated July 2017.


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