Increasing age is a significant cause of subfertility in women. As a woman gets older, the number of eggs in her ovaries decreases rapidly. Those remaining are of a poorer quality. Many women choose to delay starting a family perhaps due to career or financial reasons. However a woman's fertility rapidly declines once she enters her 30's. For example, a healthy 30-year-old woman has about a 20% chance per month to get pregnant. By age 40, however, this reduces to about 5% per month.
Alcohol, smoking, drug use, and excess weight are all common causes of subfertility. Adopting a healthy lifestyle is the first step in optimising your chances of becoming pregnant. These are the only risk factors for subfertility that you have the power to change.
Stress, anxiety, excessive weight loss/ weight gain and strenuous exercise may all cause irregular ovulation. Hormonal imbalances such as high levels of the hormone Prolactin may also affect ovulation. Polycystic Ovary Syndrome (PCOS) is a common female health problem in which there is an imbalance in a woman's hormone levels. It is characterised by the presence of small cysts on the ovaries and greater than normal levels of male-type hormones in the body. Women with PCOS usually experience irregular ovulation which reduces chances of pregnancy.
The Fallopian tubes allow the transport of the released egg from the ovary into the womb. Anything that blocks these tubes, and hence the egg from travelling, can result in fertility difficulties. Causes of blockage include scarring of the tissue inside the tubes from previous surgery or from Pelvic Inflammatory Disease (PID).
Endometriosis is a condition where the endometrial tissue, found in the lining of the womb, grows in areas outside of the womb. This tissue can be found on the ovaries, in the Fallopian tubes, on the bowel and in the pelvic cavity. Each month, hormones released by the body cause this tissue to build up causing pain, inflammation and scarring.
Some women experience involuntary tightening of the walls of the vagina during sex. This is called 'vaginismus'. Vaginismus can interfere with sex by causing pain and soreness during penetration and for some women it can make penetrative sex impossible. If penetrative sex is not possible, pregnancy cannot occur. (For further information on vaginismus please download our information leaflet (pdf).)
In many cases no reason for subfertility can be detected. Sometimes a combination of the above factors leads to subfertility.