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There are multiple factors to consider when choosing a birth control: your reasons for seeking birth control, your medical history, whether you can remember to take a pill every day. But should you also consider cancer risk when deciding to take the birth control pill?

Here¡¯s what researchers know: Oral contraceptives ¡ª better known as the pill ¡ª may affect a woman¡¯s chances of developing breast, colorectal and gynecologic cancers like ovarian cancer and endometrial cancer. In some cases, that means a bigger chance of cancer. In others, it means protection against cancer.

The reason? Most oral contraceptives contain man-made versions of the female sex hormones estrogen and progesterone. Taking the pill changes your hormone levels, which can trigger or ¡ª in other cases ¡ª prevent some types of cancer.

Ahead, gynecologic oncologist , tells us more about birth control pills and cancer risk.

Birth control pill basics

To understand the birth control pill, it can help to go all the way back to elementary school health class.

A female¡¯s menstrual cycle prepares her body for a possible pregnancy. Over the course of a month, an egg matures and is released from the ovaries. When there isn¡¯t a pregnancy, endometrial lining is released. Then, the cycle repeats.

When you add birth control into the picture, this cycle stops.

The pill uses hormones to suppress ovarian function by blocking a cycle that is initiated by the brain and impacts the ovaries. These hormones stop the feedback loop between the brain and body which halts not only ovulation, but also ovarian function, Wilke says.

¡°To put it simply, because of the hormones from the pill, the brain thinks, ¡®Oh, there's a lot of hormones around, the ovaries don't need to release any more,¡¯¡± she says.

Birth control uses

Birth control can be used for a variety of reasons aside from its namesake.

For example, Wilke notes the birth control pill can be used for:

• Contraception
• Limiting periods, which can be helpful for those with heavy bleeding, pelvic pain or period-related mood disorders
• Managing endometriosis and pelvic pain
• Managing ovarian cysts
• Managing premature ovarian insufficiency
• Acne and hormonal regulation

The pill may lower ovarian, endometrial and colorectal cancer risk

The  writes that ¡°studies have provided consistent evidence¡± that women taking the birth control pill have a reduced risk of ovarian cancer, endometrial cancer and colorectal cancer.

¡°We know that patients who take birth control actually have a lower risk of ovarian cancer, and in some studies that risk reduction is actually pretty high; it's around 50%,¡± Wilke says.

Studies also suggest the pill may protect against ovarian cancer in women with BRCA genetic mutations, according to the NCI.

Even more good news? Your risk for endometrial and ovarian cancer is reduced more the longer you take the pill, and these protective benefits may last years after you stop taking it. For example, the pill has been linked to a decreased risk of ovarian cancer ¡°for up to 30 years after a woman stops using oral contraceptives,¡± the NCI writes.

Researchers are still exploring exactly why this lasting protection occurs, but there are some ideas. For ovarian cancer, this risk reduction may be because women who take the pill ovulate fewer times than women who don¡¯t take the pill. The more times you ovulate over your lifetime, the more hormones you¡¯re exposed to.

¡°There's something about cumulative ovulation cycles over time that increases the risk of ovarian cancer,¡± Wilke says, noting that other events that stop ovulation, such as multiple pregnancies and breastfeeding for an extended time, are also associated with lower ovarian cancer risk. ¡°There's something about the ovulatory event and what the fallopian tubes essentially bathe in that leads to carcinogenesis over time. So, if you decrease the number of ovulatory events over a woman's lifetime, then you also reduce her ovarian cancer risk.¡±

The pill may increase breast cancer risk ¡ª but just slightly

Studies have shown that having ever taken the pill increases your risk of breast cancer. However, your risk decreases after you go off the pill. Research has found your breast cancer risk level is back to normal about 10 years after you stop taking the pill, according to the NCI.

Plus, if you¡¯re in your teens, 20s, 30s or early 40s ¡ª the ages when most women take the pill ¡ª your cancer risk is low. So, that potential increased risk from taking the pill is even smaller.

¡°In young women that are using the birth control pill, the risk of it leading to any cancer is extremely low. Its use has been demonstrated to be associated with a reduction in the risk of ovarian, endometrial and colorectal cancers,¡± Wilke says.

What to know about observational studies

Much of the information we currently have on birth control pills and cancer risk was determined through observational studies.

¡°An observational study essentially means that there is no intervention; we watch what happened over time,¡± Wilke says.

Observational studies help researchers see patterns, but they can't be used to definitely say that one factor caused something to happen. This is because these studies have so many variables.

Say, for example that you lose weight after eating a specific diet, working with a dietitian, exercising and strength training. It would be really hard to say for sure that one of those factors was responsible for your weight loss, Wilke explains.

¡°You will never know exactly which one of those things led to the outcome because it's all those decisions together,¡± she says.

The same is true of the studies exploring birth control and cancer risk.

¡°When we're comparing groups that took the birth control versus groups that didn't, there are different reasons that people make those decisions. It's impossible to look back and say the birth control pill was definitely the one thing that made the difference because there's a host of other decisions made that could also impact the outcome,¡± she says.

Don¡¯t lose sight of other cancer risk factors

Birth control pills are only one of many factors that can influence your cancer risk.

Another important consideration? Knowing your family history of breast, ovarian, endometrial, and colorectal cancer and getting genetic testing when appropriate, Wilke says.

¡°If you have a family member that you know has a genetic variant that increases the risk of cancer, then you should consider getting tested yourself,¡± she says. ¡°Those are the people that I worry most about developing ovarian cancer, and there are things that they can do about it.¡±

If your genetics put you at high risk for ovarian cancer or endometrial cancer, Wilke suggests talking to your care team about options, including risk-reducing surgery.

¡°For those women, I would always recommend having a more broad discussion about their options as opposed to just turning to the birth control pill for their risk reduction,¡± she says.

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