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The surprise upside of the pill – ovarian cancer protection

Key points 
  • Oral contraceptive pill use reduces ovarian cancer risk by 30% to 50% 
  • The longer the pill is used, the greater the protection 
  • Protection persists for more than 20 to 30 years after stopping 
  • Estimated ~200,000 ovarian cancers prevented worldwide to date.  
  • Benefits need to be weighed against some increased risk for other cancers (breast and cervical), cardiovascular conditions and stroke  


Oral contraceptives have been life-changing for millions of women around the world: offering effective birth control, managing periods and period pain, lightening bleeding, regulating the menstrual cycle, clearing acne, and reducing the symptoms of conditions like endometriosis and polycystic ovary syndrome.   

Less well known are its benefits in protecting against some cancers – including ovarian.  

Of course, ‘the pill’ has not been without controversy or risk, and its benefits must be weighed up against risks – including increased risk of other cancers, particularly for some higher-risk groups.  

The pill is protective against ovarian cancer 

The combined oral contraceptive (COC) pill – which includes oestrogen and progestogen – has been shown in large-scale studies to provide strong protection against ovarian cancer, reducing risk by 30 per cent to 50 per cent1. This protective effect increases with prolonged use and can last for decades after a woman stops taking the pill.  

It’s important to note that while there is robust evidence that COC pill use reduces the risk of ovarian, as well as endometrial (uterine) and bowel cancer, it is not prescribed as a broad prevention strategy because of the moderate counter risks associated with some other cancers, stroke, and cardiovascular conditions in some individuals.   

But given the low survival rates for ovarian cancer, it is unsurprising that researchers keep coming back to learn more about this risk reduction effect. It offers exciting potential for further research and may offer clues for proactive prevention measures for some women.  

What is the evidence?  

One of the large-scale studies published in the trusted medical journal, The Lancet2 found the pill can reduce the risk of ovarian cancer by about 30 per cent.  

The study tracked more than 100,000 women in 21 countries and found the longer that women had used oral contraceptives, the greater the reduction in ovarian cancer risk. Published in 2008, the study suggested that oral contraceptives had prevented some 200,000 ovarian cancers and 100,000 deaths from the disease at that time.  

These initial findings have since been replicated in many studies, most recently in 2025 by South Australian researchers, including a previous OCRF-funded researcher Prof Martin Oehler.3  

Which oral contraceptives provide protection?

Oral contraceptive pills come in different formulations. Combined oral contraceptives (COC) contain two hormones, oestrogen and progestogen, and the most robust data for ovarian cancer protection comes from this pill type.  

Progestogen-only pills (POPs) may offer some protection, but there is not enough evidence to point to this, according to the body of research.  

It’s worth noting that the pill formulation has changed since its inception – the oestrogen dose is lower in modern pills. Some newer versions also include a more natural form of oestrogen called oestradiol, compared to the predominant ethinyloestradiol,4 which may improve safety and efficacy – but more research is needed to investigate how any risks or benefits compare with earlier versions.  


How does the pill protect against ovarian cancer? 

The main theory about how the pill works to protect against ovarian cancer is by blocking ovulation and therefore minimising cell damage that occurs as a result.  

Each ovulation ruptures the top cell layer of the ovary, triggering inflammation, and DNA repair to restore the structural integrity of the ovary. Repeated exposure over time to this cycle creates a cumulative increase in the risk of DNA changes that may lead to cancer. By blocking ovulation, oral contraceptive pills reduce lifetime ‘hits’ and could be helping to lower the risk of ovarian cancer.5

Researchers say women should be informed of the benefits   

In a 2015 published study, a long list of international experts including leading Australian ovarian cancer researchers agreed that women, including those at increased genetic risk of ovarian cancer, should be made aware of the protective benefits of oral contraceptives.6

The authors also highlighted an urgency to understand the mechanisms providing the benefit in oral contraceptives, given the increasing use of intrauterine devices.  

“Oral contraceptives provide lasting risk reduction in both the general female population and in women who carry germline BRCA1 or BRCA2 mutations, with duration of oral contraceptive use being proportional to the decrease in risk,” said the authors, including Prof David Bowtell and Prof Clare Scott, two of Australia’s leading experts in the field.  

“It is important that women, especially those at increased genetic risk of ovarian cancer, are aware of this benefit,” said the authors. 

“Further research is needed to understand the basis of protection provided by oral contraceptive usage, particularly at a time when intrauterine devices are increasingly favoured for contraception in younger women." 

Weighing up the risks  

Large-scale studies have shown slight temporary increases in breast cancer and cervical cancer associated with use of the pill, with risk declining when use is stopped.  

For cervical cancer, the risk is only in women who already have the human papillomavirus (HPV) which causes almost all cervical cancers, and for which there is now a vaccine. The lifetime risk of breast cancer is approximately 1 in 8 (about 13%), while ovarian cancer risk is around 1 in 70 (about 1.4%).  

The consensus, including in this study in the American Journal of Obstetrics and Gynaecology7  is that on balance the reduced risk of ovarian, endometrial and colorectal cancers of the pill outweighs the risks of breast and cervical cancer.  

Who should be careful? 

While the pill offers protection from ovarian cancer, cancer-causing changes in the BRCA1 and BRCA2 genes increase the risk of breast and cervical cancer. For BRCA1 carriers the increased risk of breast cancer is roughly three per cent per year of pill use. Long-term use – more than 10 years – is linked to about a 30 per cent relative increase in triple-negative breast cancer in BRCA1 carriers. For these women, therefore, the equation is complex.

The bottom line - speak to your GP or specialist  

On balance, for most women the protective benefits of the pill will outweigh the risks, especially in terms of cancer. As with all prescription medicines, women should make an informed decision in discussion with their GP or specialist. Meanwhile, we continue to watch the ongoing research closely. 

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The Ovarian Cancer Research Foundation acknowledges the Traditional Custodians of the lands upon which we work, strive, and learn, the Wurrundjiri Woi wurrung and Bunorung Boon wurrung peoples of the Kulin Nation. We pay our respects to Elders past and present, and extend this respect to all Aboriginal and Torres Strait Islander peoples in Australia and beyond.