Cervical cancer risks and causes
This page is about the risk factors and causes of cervical cancer. You can find the following information
- A quick guide to what's on this page
- How common cervical cancer is
- What a risk factor is
- HPV infection
- Other sexually transmitted infections
- A weakened immune system
- The pill
Human papilloma virus (HPV) is the major cause of cervical cancer. There are many different types of HPV. Some types of HPV cause genital warts and are sometimes called the genital wart virus. The types of HPV that cause warts do not usually cause cell changes that develop into cancer. Some other types of HPV are considered high risk for cancer of the cervix. HPV is passed on from one person to another through sexual contact.
Women who get cervical cancer have had past infections with HPV. High risk types of HPV can cause changes in the cells covering the cervix that make them more likely to become cancerous in time. But most women infected with these viruses do NOT develop cervical cancer. So other factors must also be needed.
Women who smoke are more likely to get cervical cancer than those who don't. Taking the pill could increase a woman’s risk of cervical cancer. It is not clear why this is. Women with a weakened immune system are also more likely to get cervical cancer and so are those who have had a large number of children.
You can view and print the quick guides for all the pages in the about cervical cancer section.
Around 3,100 women are diagnosed with cervical cancer in the UK each year. Overall, about 2 out of every 100 cancers diagnosed in women (2%) are cervical cancers. But it is the most common cancer in women under 35 years old.
More than 4 million women are invited for cervical screening each year in England. Around 1 in 100 women screened has a moderate or high grade abnormality (1%). Early treatment can prevent these cervical changes developing into cancer.
Anything that increases your risk of getting a disease is called a risk factor. Different cancers have different risk factors. This page discusses the risk factors for cervical cancer. Even if you have one or more of the risk factors below, it does not mean that you will definitely get cervical cancer.
Human papilloma virus (HPV) is the major cause of the main types of cervical cancer – squamous cell cancer and adenocarcinoma. There are over 100 different types of human papilloma virus (HPV). At least 40 types are passed on through sexual contact. Some types are called the wart virus or genital wart virus because they cause genital warts. The types of HPV that cause warts do not usually cause cell changes that develop into cancer.
At least 15 types of HPV are considered high risk for cancer of the cervix - they include types 16 and 18. These 2 types cause about 7 out of 10 cancers of the cervix (70%). If you have persistent infections with high risk types of HPV, you are more at risk of developing pre cancerous cervical cells or cervical cancer.
HPV is common. Most sexually active women will come into contact with at least one type of HPV during their lifetime. But for most the virus causes no harm and goes away on its own. So other factors must be needed for cancer to develop. If men use a condom during penetrative sex, this reduces the risk of a woman becoming infected with HPV.
There are now vaccines to prevent HPV infection. All girls aged 12 or 13 in the UK are routinely offered the HPV vaccine at school. These vaccines protect against the strains of HPV that are most likely to cause cervical cancer. But they don't protect against all strains. It will take some years before the introduction of the vaccine has a major effect on reducing the number of cases of cervical cancer. So it is still important to carry on with cervical cancer screening.
One study has shown having both herpes and HPV infection may increase the risk of cervical cancer, after taking into account HPV infection and the number of sex partners women had and their use of the pill. However, another more recent study has shown no link.
Another study looked at infection with HPV and chlamydia (pronounced klah-mid-ee-ah). The study found that the risk of squamous cell cancer around doubled in women with both infections.
If you smoke, you are more likely to develop squamous cell cervical cancer. Researchers have found cancer causing chemicals (benzyrene) from cigarette smoke in the cervical mucus of women who smoke. They think that these chemicals damage the cervix. There are cells in the lining of the cervix called Langerhans cells that specifically help fight against disease. These cells do not work so well in smokers.
If you have a high risk type of HPV infection and smoke, you are twice as likely to have pre cancerous cells in your cervical screening test, or to get cervical cancer. The Langerhans cells are less able to fight off the virus and protect the cervical cells from the genetic changes that can lead to cancer.
A type of study called a meta analysis combines the results of several individual studies looking into a particular topic. This is more reliable than the results of a single study. A recent meta analysis showed the risk of squamous cell cervical cancer is doubled in women who currently smoke. An estimated 7% of cervical cancers in the UK are linked to smoking.
If you have a weakened immune system, then your risk of many cancers, including cervical cancer, is higher than average. People with HIV and AIDS, or people taking drugs to suppress their immune systems after an organ transplant, are more at risk of developing cervical cancer if they also have HPV infection. However, if you have had an organ transplant and have regular cervical screening, your risks will be the same as the general population.
This is because a healthy immune system normally protects you from cells that have become abnormal. Your immune system will kill off the cells and so prevent them from becoming cancerous.
Research that looked at a number of studies together shows that taking the pill could increase a woman's risk of developing cervical cancer. It is not clear why this is. The researchers took account of other factors, such as the number of sexual partners, smoking, and most importantly, infection with HPV. Researchers suspected that there was a link with taking the pill, but clear evidence has not come out of the studies until more recently.
Before now we thought that the pill was statistically linked to cervical cancer because women on the pill are more likely to be sexually active and so more at risk of picking up HPV. Also, they do not necessarily use barrier contraception (condom or cap) which could prevent them picking up the HPV. But now it seems that it may actually directly increase the risk.
Recent research suggests that amongst women who have taken the pill for at least 5 years, risk is almost doubled. But this is still a small risk, and it is important to know that taking the pill can help to protect you against womb and ovarian cancers.
The evidence suggests that the increased risk of cervical cancer begins to drop as soon as you stop taking the pill. After 10 years the risk is the same as if you had never taken it. The important thing to remember is that regular screening can pick up changes in the cervix before they develop into a cancer. Obviously, screening is now very important for women taking the pill.
Some research suggests that women with partners who have been circumcised are less likely to get cervical cancer. This may be because men who are circumcised are less likely to carry HPV infection. This research took into account different factors relating to sexual behaviour.
You will quite often hear that women who started having sex young or women who have a lot of different sex partners are more likely to get cervical cancer. But really, this is only true because the earlier you start having sex and the more men you have sex with, the more likely you are to pick up an infection with a high risk (cancer causing) human papilloma virus (HPV). And so then you are more at risk of developing cervical cancer.
It is not correct to say that women who get cervical cancer have it because they were promiscuous (slept around). After all, you could have only slept with one man and still caught the virus if he had it. If he's had lots of partners, that will increase your risk, because it indirectly exposes you to possible sexual infections from lots of other people.
Health education may help women reduce their exposure to HPV and so reduce the risk of cervical cancer. Some studies have shown that teaching women about healthy sexual behaviour, such as using condoms, avoiding sex when they are young, learning how to talk to their partner about safe sex and reducing the number of sexual partners, can help them behave in ways that may lower their cervical cancer risk.
There is no evidence to say that pregnancy is linked with the risk of cervical cancer. Women who are pregnant may have cervical screening and so this can lead to women being diagnosed with pre cancerous changes or cervical cancer while they are pregnant.
Women who have had children are at an increased risk of squamous cell cervical cancer compared to those who haven't. Women who have had 7 or more children have double the risk of squamous cell cervical cancer compared to women who have had only 1 child. Having your first baby before the age of 17 also gives a higher risk, compared to women who had their first baby after the age of 25. There is no link to adenocarcinoma. This research took into account HPV infection, number of sexual partners and the age women were when they first had sex. And they found that HPV infection did not explain the increase in cervical cancer. However the reasons for this are unclear.
One study showed that women with a first degree relative (mother, sister or daughter) diagnosed with adenocarcinoma or squamous cell carcinoma of the cervix have around double the risk of developing cervical cancer, compared to women without a family history. But we don’t know whether this is linked to faulty genes, or whether it is due to common lifestyle factors and it is just one study.
Around 1 out of 100 cervical cancers in women in the UK (1%) are thought to be linked to occupation. This is due to exposure to a chemical called tetrachloroethylene. This is used in dry cleaning and metal degreasing.
It has also been shown that women living in the poorest (most deprived) areas of the UK are more likely to develop cervical cancer than those living in more wealthy areas.
Diethylstilboestrol is also called DES. It is a drug that doctors gave women in the 1940s to 60s to stop them having a miscarriage. The daughters of women who took DES during their pregnancy are more at risk of developing a rare type of cervical cancer called clear cell adenocarcinoma. DES hasn't been used for 40 years and so is becoming less important as a risk factor.
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