The most commonly used and prescribed birth control pill in the U.S. was classified by the International Agency for Research on Cancer (IARC) at the World Health Organization (WHO) as carcinogenic.
In 2008, the IARC released its report on combined oral contraceptives, which determined that the female birth control pills were a Group 1 carcinogen—placing them in the highest hazard classification, alongside tobacco, alcohol and asbestos.
While the classification was made over a decade ago, viral posts on social media have claimed that the birth control pill has only just been deemed a human carcinogen.
To shed light on the what the classification means and why such pills are still widely in use, Newsweek spoke to the IARC and various experts in the field to get to the bottom of the issue.
How Many Women Use Birth Control Pills?
Many women between the ages of 15 and 49 use birth control pills in America. The Centers for Disease Control and Prevention (CDC) say that 14 percent of American women in this age range use the pills, although other sources put the number at 25 percent.
There are three types of widely prescribed oral contraceptive pills: the combined estrogen-progesterone pill, the progesterone-only pill, and continuous or extended-use pills. Of these pills, the combined pill is the most commonly used by women in America.
Combined oral contraceptives are taken to help prevent pregnancy, by stopping ovulation from happening as well as via other means, and may also be taken in the treatment of anemia by reducing menstrual bleeding, avoiding pain from endometriosis, and managing acne and other hormone-related issues.
What Does The WHO Classification Mean?
The IARC’s 2008 classification of combined oral contraceptives, shared with Newsweek, detailed that there was “sufficient evidence” they can “cause cancer of the breast, in-situ and invasive cancer of the uterine cervix, and cancer of the liver.”
However, the report added that for cancer of the endometrium, ovary, and colorectum, “there is evidence suggesting lack of carcinogenicity.”
While there has been serious alarm raised on social media platforms like TikTok about birth control pills in light of the classification, the IARC told Newsweek that it “conducts hazard identification only,” meaning whether “an agent is capable of causing cancer at least at some exposure levels or circumstances.”
This means the IARC does not “conduct a risk assessment,” which would assess “the chance of an agent causing cancer at a given exposure level or circumstance.”
There has previously been “confusion and other common misconceptions” about the classifications the IARC provides, a spokesperson told Newsweek, prompting the program to share a report in 2019 to explain how its classification system works, and what they each mean.
The Group 1 classification, which the combined oral contraceptive pill was placed in, is described in the report as when there is “convincing evidence that the agent causes cancer in humans.”
However, the report notes that a Group 1 classification, or any other given by IARC, “does not measure the likelihood that cancer will occur at a particular level of exposure to the agent.”
This means that while the IARC found that combined oral contraceptives are carcinogenic to humans, this does not determine how high the risk of developing cancer is by taking the pill at the usually prescribed dose.
Other Findings on Carcinogenicity of Birth Control Pills
Other researchers have found links between the combined contraceptive pill and an increased risk of developing breast cancer, but also that the pill may prevent endometrial and ovarian cancers in some cases—prompting researchers to determine the pill has a “net protective effect” after a study revealed their use prevented cancer in more cases than increased the risk.
“More recent evidence has clarified that if there is an increase in breast cancer, the magnitude of the increase is small and is limited to recent users, meaning that the risk dissipates over time after stopping oral contraceptives,” Dr. Daniel Grossman, a professor of obstetrics, gynecology and reproductive sciences and director of the Advancing New Standards in Reproductive Health, at University of California, San Francisco, told Newsweek.
A study by the Royal College of General Practitioners’ Oral Contraception, which followed over 45,000 women for up to 44 years found that “most women who choose to use oral contraceptives do not expose themselves to long-term cancer harms; instead, with some cancers, many women benefit from important reductions of risk that persist for many years after stopping.”
Another study by U.K. Biobank of over 250,000 women found that oral contraceptives “can dramatically reduce women’s risk of ovarian and endometrial cancer, whereas their effect on lifetime risk of breast cancer is limited.”
Why Is the Combined Birth Control Pill Still in Use?
Questions have been raised online about why the combined birth control pill is still being used when they are categorized at the same level of carcinogenicity as tobacco.
“Packaging for hormonal contraception includes warnings about their most common risks,” Dr. Eleanor Schwarz, a professor at the Philip R Lee Institute for Health Policy Studies at the University of California, San Francisco, told Newsweek.
She added that the number of patients “harmed by contraceptive pills is truly like a drop of water compared to the ocean of suffering and premature deaths that are cigarette-related.”
“The balance is generally favorable re: cancer, and is also favorable with respect to health benefits and overall mortality,” Carolyn Westhoff, a professor of obstetrics and gynecology at Columbia University, told Newsweek.
“Combined oral contraceptives are well known to slightly increase risk of several cancers and they also decrease the risk of other cancers,” she added. “In contrast, smoking has no health benefits.”
Therefore, the reason the birth control pills remain available despite the carcinogen classification is because of “the overall low additional risk of breast cancer associated with oral contraception use,” Dr. Abigail Liberty, a professor of obstetrics and gynecology, at Oregon Health & Science University’s School of Medicine, told Newsweek.
She added that they also have potential benefits for ovarian cancer prevention and management of menstrual disorders, as well as contraception.
Combined oral contraceptives also have notes listed beside them on the American Cancer Society website to highlight that those medicines have been associated with some cancer protection and some cancer risk, Liberty said.
“It is incredibly important that providers discuss risks of all medications with their patients, but without fearmongering and with the utmost respect for the patient’s perception of risk,” she added.
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