Causes of infertility

Causes of infertility

Infertility is the inability to conceive after one year of regular unprotected intercourse. This definition is reduced to six months for:

  • Women over 35
  • Women with a history of painful periods and/or irregular cycles
  • Women with pelvic inflammatory disease
  • Couples who know that the male partner has a low sperm count

Around 1 in 6 couples have difficulty in achieving a pregnancy and this proportion is increasing, largely for two reasons: firstly, women are delaying starting their families and secondly, sperm counts are falling.

The earlier you seek help, the greater your chances for success. If you and your partner have been trying to conceive without success, have been diagnosed with infertility or are in a same sex relationship, we recommend seeing a specialist as soon as possible.

For more information or to make an appointment, please click here.

There are many reasons why you might be having difficulty getting pregnant but broadly speaking they are due to problems of sperm quality, problems of producing an egg (ovulation) and egg quality, problems with the fallopian tubes or a combination of these factors or other factors.

Common sperm problems

In many parts of the world sperm counts are falling. As a result, we are seeing more men with:

  • Too few sperm
  • Not enough motile sperm
  • Minor genetic problems that affect sperm counts and quality
  • Genetic problems or past infection that has blocked the tube which connects each testicle with the penis (vas deferens).

Common egg problems:

  • Polycystic ovary syndrome (PCOS), resulting in infrequent ovulation
  • Being over or underweight, resulting in irregular ovulation
  • Taking medications that affect ovulation
  • Increasing age. Unfortunately, as a woman gets older, the quality of her eggs decreases and conception is more difficult.

Common Fallopian tube problems:

  • Past pelvic infection
  • Past pelvic surgery


Endometriosis is a common condition where the cells that line the womb occur outside the womb in the abdomen. Moderate and severe disease can affect the function of the ovaries and the fallopian tubes but even mild endometriosis can have a negative effect on a couple’s fertility, possibly by subtle effects on the function of sperm or the fallopian tubes.

Unexplained infertility

In a proportion of couples we cannot find an obvious cause for their subfertility and this is termed “unexplained infertility”. It does not mean that there is nothing wrong, it just reflects our knowledge at the present time, and it might be due to a subtle problem with one of the hundreds of things that are required for successful conception and implantation.