The causes of infertility are not obvious just by looking at someone. The underlying problem can be something inside the body of the female partner, such as a blocked fallopian tube, or within the male partner, such as a low sperm count. Both men and women can have hormone imbalances that affect production of eggs or sperm. Sometimes, a relatively mild problem occurs in both partners and the combination of factors leads to infertility.
Fertility testing can investigate the cause of infertility in healthy couples who have been trying to have a baby for between 12 and 24 months without success. These tests can reveal that infertility issues affect men and women equally; it is up to testing to reveal where the problem lies so that both partners can deal with it and work with infertility specialists to work out the best way forward. This may involve considering various forms of infertility treatment
Male fertility tends not to decline with age in the same way that female fertility does (see below). Men of all ages can have problems that make them infertile, including:
A blockage in the testes: some men have a blocked tube in the testes so cannot transport sperm to the penis for ejaculation. Surgery to remove a blockage may be possible, but if not, surgical sperm retrieval can be used with IVF/ICSI.
The factors that cause all of these problems can be genetic (so present from birth) or they can be acquired during life. Some drug treatments, some infections (mumps, for example, which causes inflammation in the testes) and chronic diseases such as diabetes can all cause male infertility.
One of the major reasons for infertility in women is age. All women become infertile during the menopause, which happens anytime between the ages of 45 and 55. Some infertility clinics around the world have created controversy by using eggs donated by a younger woman in combination with IVF to enable women to become pregnant into their 60s, but this is ethically unacceptable to many individuals, cultures and religions.
Causes of infertility in women under 45 include:
Age again: although a woman does not become completely infertile until the menopause, her fertility declines rapidly after the age of 35. This is shockingly young to some women who leave having a baby until later in life.
Body weight: being obese or seriously underweight can both lead to infertility. Women who are very underweight usually do not ovulate and so do not have periods. Regaining a healthy weight can make natural conception possible.
Hormone imbalance: the menstrual cycle and ovulation are controlled by several hormones produced by the brain. A problem with the pituitary gland or hypothalamus, or the thyroid, can all affect hormone production and can cause a woman to produce no eggs, or to have irregular ovulation. Hormone treatments and/or fertility drugs can help.
Blocked fallopian tubes: if the fallopian tubes are both blocked, the egg cannot move down from the ovary into the uterus to meet up with sperm from the male partner. Blocked tubes may result from sexually transmitted diseases such as gonorrhoea that lead to pelvic inflammatory disease. Clearing the blockage can be done surgically but many women with this type of infertility can benefit from IVF.
Endometriosis: this arises when the material that usually lines the uterus grows elsewhere in the abdomen. It can stick to the intestines, the kidneys, the bladder and urethra and the outside of the uterus and fallopian tubes, and it can surround the ovaries. It expands each month as oestrogen levels rise, causing pain and creating adhesions and more inflammation. Women with endometriosis are not always infertile but many need infertility treatments such as IUI or IVF to get pregnant.
Polycystic ovary syndrome (PCOS): this is caused by the development of cysts on the ovaries, which leads to an imbalance of hormones. Women affected produce too much progesterone, and develop facial hair, tend to be overweight and often face infertility issues. Losing weight and having hormone treatments can help, but women with PCOS may need infertility treatments.