Using even newer forms of birth control pills and IUDs which release hormones is associated with a small—but significant—increased risk of breast cancer, according to a large new study published by Danish scientists.
With studies like this, it’s always important to note that correlation isn’t the same thing as causation. But it’s noteworthy because of its scope and the fact that it’s one of the first efforts to examine modern birth control methods (which contain lower levels of estrogen than earlier ones did) and possible associations with breast cancer. Previous studies had linked older hormonal birth control regimens with an increased breast cancer risk.
The researchers tracked nearly 2 million Danish women over the course of a decade. They found that, for every 100,000 women, there were 68 cases of breast cancer per year in women using hormonal birth control versus 55 annual breast cancer cases among those who didn’t.
There are several important caveats to keep in mind here. For one, the Danish population may not be entirely representative; and doctors overwhelmingly endorse hormonal birth control as a safe and easily accessible contraceptive option for women. Health experts responded to the study with caution, recommending women to consult with their physicians before making any major changes to their health regimens.