Can Birth Control Prevent Cancer? What You Need to Know About the Latest Research

IUD clinic
A health worker inserts an intrauterine device (IUD) at a reproductive health clinic in the Philippines on January 12, 2016. REUTERS/Janis Alano

By giving women the power to control when or if they have children, birth control changed the world. But using birth control for a long period of time may also increase a woman's risk of deveIoping cervical cancer—unless it's an intrauterine device (IUD), according to one new review paper published Tuesday. That form of birth control may decrease the risk of cervical cancer.

The link between birth control and cancer is complicated. It's long been suspected that IUDs may protect women against cervical cancer; the American Cancer Society even mentions it on its website. This new paper, published this month in Obstetrics & Gynecology, found that an IUD could possibly decrease the risk of cervical cancer, but it's still impossible to say for sure, according to Victoria Cortessis, one of the authors of the paper.

The widespread use of birth control means that even a slight reduction in risk is worth knowing about. The use of long-acting contraception—of which an IUD is the most common type—has increased fivefold in the last 10 years, according to CDC data. "The potential is enormous if a quarter to half of women can be spared cervical cancer by their contraceptive choices," she said.

The researchers found that an IUD could reduce the risk of cervical cancer by about a third. But that reduction would pale in comparison to the effect of regular screenings.

The number of new cervical cancer cases diagnosed each year has declined over 50 percent since 1975, due in part to screenings and the introduction of the Gardasil vaccine, which first got FDA approval in 2006. Gardasil protects against forms of the human papillomavirus, a sexually transmitted disease also referred to as HPV.

Certain strains of HPV have been strongly linked to cancer, so screening usually includes a test to see whether cervical cells have the virus in them. (The Pap smear, another common screening test, is based on the presence of abnormal-looking cervical cells in a sample.) People can be infected with HPV without developing cervical cancer—but if the viral infection does not eventually clear up, a cancer may grow. "Screening is everything," Cortessis said. "If a woman has one lifetime screening visit in her entire life, her risk is much lower."

The problem is that many women aren't screened, creating a need to find other ways to reduce the risk of cervical cancer. "In a population where every woman was perfectly screened, we would see no cervical cancer," said Cortessis. Screening would have to be followed by appropriate follow-up care, of course, but if those both happened, the IUD would show no benefit, she explained. Then again, if no women were screened, the cancer-reducing benefit of the IUD would be even stronger. "And we're in the middle," said Cortessis.

Gardasil box
An illustration picture shows a Gardasil anti-cervical cancer vaccine box displayed at a pharmacy in Strasbourg on November 25, 2013. REUTERS/Vincent Kessle

Perfect screening hasn't happened yet—even in the U.S.—and many people in the developing world don't have wide access to the vaccine. When Cortessis looked only at studies that controlled for the amount of screening, she and her colleagues found that women who had better access to cancer screening, as defined by the number of screenings they had in their life, still got cervical cancer about a third less often.

That said, many of the studies in the new analysis are relatively old; there's a vaccine for the virus that causes cervical cancer now. Screening is getting increasingly nuanced. And touting IUDs as the best way to protect against cervical cancer would be wrong, noted Dr. Mark Schiffman, a cervical cancer expert at the National Cancer Institute. "The critical ways to prevent cervical cancer are a judicious combination of HPV vaccination and HPV-based cervical screening," he said—even in developing countries with fewer resources. "These are much more powerful preventive interventions than putting in an IUD for the purpose of cervical cancer reduction."

The bottom line, then, is not that IUDs can prevent cervical cancer, Schiffman said. "They're just better with regards to risk than using long-term oral contraceptives."