Reality check: Does the birth control pill protect women from cancers?

Genetics and lifestyle have a much greater impact on breast cancer risk than the birth control pill, the Canadian Cancer Society says.
Genetics and lifestyle have a much greater impact on breast cancer risk than the birth control pill, the Canadian Cancer Society says. Getty Images

Women worldwide have been relying on the birth control pill to prevent unwanted pregnancies since the 1960s. Despite its known benefits, women have also been warned of the increase in potential health risks associated with taking hormonal-based contraceptives, one of them being cancer.

However, a new study by the University of Aberdeen suggests that while there is a slight risk in developing breast and cervical cancers, the birth control pill might have a “strong preventative effect” for staving off ovarian, endometrial and bowel cancers for up to three decades.

“These results from the longest-running study in the world into oral contraceptive use are reassuring,” Dr. Lisa Iversen, research fellow at the Institute of Applied Health Sciences at the University, says in a statement. “Specifically, the pill users don’t have an overall increased risk of cancer over their lifetime and that the protective effects of some specific cancers last for at least 30 years.”

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Researchers followed 46,000 women since the study (called the Oral Contraception Study) was created by the Royal College of General Practitioners (RCGP) in 1968.

Among their findings, researchers found that taking the pill for any length of time decreased women’s chances of endometrial cancer by 34 per cent, ovarian cancer by 33 per cent and bowel cancer by 19 per cent.

The risk of breast cancer only increased by four per cent, but disappears five years after stopping the pill.

They also concluded that for every three women who had developed ovarian and endometrial cancer, one had been protected by the pill. As for bowel cancer, the pill prevented about one-fifth of the cases.

As well, taking the pill during reproductive years was found to not increase the risk of producing new cancers later in life, which is the time when more cancers typically occur.

“This is not to advocate that women should be given the pill as a preventative measure against cancer as we know that a minority of women do have adverse health effects as a result of taking the pill,” Helen Stokes-Lampard, chair of the RCGP, says in a statement.

“Ultimately decisions to prescribe the pill need to be made on a patient by patient basis, but this research will be useful to inform the conversations we have with our patients when discussing various contraceptive options that are available.”

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What others are saying

All in all, the findings of the study are on par with what is known among physicians already, Dr. Rob Nuttall, assistant director of health policy at the Canadian Cancer Society says.

“This study is really focusing on the long-term impacts of using birth control in your reproductive years and it really does build on a lot of the research that we’ve seen to date,” he says.

“From a cancer perspective we do know that using the birth control pill can increase your risk for some types of cancers – mainly breast, cervical and sometimes liver cancer – but it can also protect against certain types of cancers as well, like uterine and ovarian cancer.”

(The Canadian Cancer Society says there is only a small risk increase of liver cancer for women who are hepatitis negative. However, the risk is very rare.)

What surprised Nuttall the most about the study was just how fast the risk of cancer disappears after women stop taking the pill.

“We know that the risk of cancer decreases when women stop taking the pill but studies today suggest maybe the risk goes down to zero 10 years later,” Nuttall says.

“But this paper suggests that the risk goes down [to zero] as early as five years when you stop taking it. So that risk they would have had while taking the pill is gone.”
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READ MORE: Birth control for me: Is there gender inequality in health research?

But Nuttall hopes that this study opens a more informed dialogue between doctors and their patients.

“This paper’s a good opportunity to remind people that there are other things to be considered when taking the pill – the benefits and the impact on their cancer risks.”

According to the Canadian Cancer Society’s website, for every 10,000 women who use the birth control pill there are two additional cases of breast cancer if the pill was used before the first full-term pregnancy, and about one additional case of breast cancer if the pill was used after.

However, the society also states that genetics and lifestyle tend to have a much greater impact on breast cancer risk than taking the oral contraceptive.

Other potential risks and benefits and misconceptions

Several studies throughout the years have explored the impact of the pill on women’s health.

One study published in the British Journal of Clinical Pharmacology reported in 2015 that taking the pill for five years can double the risk of developing a brain tumour, especially with progestogen-only methods.

Scientists say these pills increase the chance of glioma of the brain, which is a rare cancer, The Telegraph reports.

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In 2010, an article in the journal BMJ concluded that the pill was not associated with an increased long-term risk of death, including instances where cancer and heart disease are involved.

Another benefit researchers at the University of Gothenburg in Sweden found in 2012 was that the pill can help manage painful periods.

A study published in the BMJ last year also found that taking oral contraceptives just before or during pregnancy was not linked to major birth defects.