Causes and risk factors of womb cancer

The exact cause of womb cancer is not known. Certain risk factors may increase the chances of a woman developing it. Having one of these risk factors doesn’t mean you will develop womb cancer. Equally, if you don’t have any risk factors, you may still develop it.

These risk factors include:

  • age – the risk of womb cancer increases with age
  • hormonal factors – longer exposure to the hormone oestrogen can affect your risk of womb cancer
  • weight and physical activity
  • genetic factors (family history) – Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), increases the risk of womb cancer
  • tamoxifen – a hormonal drug used to treat breast cancer.

Other medical conditions that might also increase your risk include thickening of the womb lining, diabetes, polycystic ovary syndrome and uncommon ovarian cancers.

We can’t control many of these risk factors. But keeping to a healthy weight and being more physically active may help reduce the risk of womb cancer.

Risk factors and causes

The exact cause of womb cancer isn’t known. But there are certain things that can increase a woman’s risk of developing it. These are called risk factors. Having a risk factor doesn’t mean you will get cancer, and not having a risk factor doesn’t mean that you won’t get it. Most risk factors are linked to how much of the hormone oestrogen the womb lining is exposed to.


The risk of womb cancer increases with age.

Hormonal factors

Before the menopause, the ovaries produce the hormones oestrogen and progesterone. These help to control your periods. After the menopause, the ovaries no longer produce hormones, but women still produce some oestrogen in their body fat.

A woman’s exposure to oestrogen and how this is balanced with progesterone, affect the risk of womb cancer. When there is too much oestrogen without progesterone to balance it, the risk of womb cancer is increased.

Longer exposure to oestrogen can affect your risk of womb cancer. Factors that influence this are:

  • Starting your periods early (before 12).
  • Having a late menopause (after 55).
  • Having longer periods.
  • Having irregular periods.
  • Not having periods.
  • Hormone replacement therapy (HRT).
  • Taking oestrogen-only HRT (which contains no progesterone) or a type of HRT called tibilone (Livial®). Oestrogen-only HRT is usually only given to women who have had an operation to remove their womb (a hysterectomy).
  • Not having children, or being unable to have children.

Oestrogen in the body is low during pregnancy, and the level of progesterone is high.

Weight and physical activity

Being overweight is an important risk factor for womb cancer. After the menopause, body fat is the main source of oestrogen. Women who are overweight may have a high level of oestrogen.

One in three womb cancers may be caused by being very overweight (obese). There’s also some evidence that being less physically active can increase womb cancer risk.

Genetic factors (family history)

A very small number of womb cancers may be caused by changes to a particular gene. Genes store the biological information we inherit from our parents. If there are several close relatives on the same side of the family with bowel, breast or womb cancer, there’s a possibility that there may be a genetic link. Close relatives are parents, children, sisters and brothers.

If you’re worried about a family history of cancer, speak to your cancer doctor or GP. They can decide if you should be referred to a family cancer clinic.

There are some genetic conditions that can increase the risk of womb cancer. Women with Lynch syndrome, also known as hereditary non-polyposis colorectal cancer (HNPCC), have an altered gene that increases the risk of bowel cancer and womb cancer. Women with this gene have a 30–60% risk of developing womb cancer over their lifetime. They are screened for bowel cancer and may also have tests to check for early signs of womb cancer.

We have more information about Lynch syndrome.

Women with a rare genetic condition called Cowden syndrome have an increased risk of benign (non-cancerous) tumours and also some cancers. This includes womb cancer, but the increase in risk is small.


Tamoxifen is a hormonal drug used to treat breast cancer. It can slightly increase the risk of womb cancer, usually when it’s taken over a long period of time. But there are very clear benefits of taking tamoxifen that far outweigh this risk.

Always tell your doctor if you are taking tamoxifen and have any unusual vaginal bleeding.

Other medical conditions

Some other medical conditions may cause an increased risk of womb cancer.

Thickening of the womb lining

Endometrial hyperplasia is a condition where the womb lining becomes thicker. Symptoms include heavy periods and bleeding between periods or after the menopause. When it’s diagnosed, women have treatment and/or regular tests.


Diabetes increases a woman’s risk of womb cancer. There may also be a separate link between womb cancer and insulin, a hormone that regulates blood sugar.

Polycystic ovary syndrome (PCOS)

Women with PCOS, a condition where cysts grow on the ovaries, may have fertility problems, infrequent or no periods, or may be very overweight or diabetic. These are all linked with womb cancer risk.

Uncommon ovarian cancers

Some types of ovarian cancers called granulosa and theca cell tumours can produce oestrogen. This increases the risk of womb cancer.