Does taking birth control pills increase breast cancer risk?

In the U.S., 14% of women ages 15 to 49 are currently on the pill. Also known as oral contraception, the birth control pill — which is 99% effective at preventing pregnancy — contains hormones such as estrogen and progestin (artificially made progesterone).

“There are various types of estrogen, which is a sex hormone,” says Dr. Noran Barry, a Sharp Rees-Stealy breast surgeon affiliated with Sharp Memorial Hospital and Sharp Mary Birch Hospital for Women & Newborns. “Estrogen helps with the functioning of several organs, such as the ovaries and uterus. Estrogen also helps develop breast tissue.”

Progesterone, Dr. Barry says, is a reproductive hormone that plays a crucial role in pregnancy and menstruation.

There are two main types of birth control pills. One includes both estrogen and progestin, and another contains only progestin. When progestin is used in birth control, the hormone stops ovulation from occurring. Some women take progestin-only birth control pills due to medical reasons, such as being at risk of forming blood clots, which can increase with the use of estrogen.

Birth control and breast cancer

Whichever kind of birth control a woman takes, she may wonder whether it increases the risk of developing breast cancer. The answer can be complex.

Results from several studies show that women who take birth control pills may have a slightly higher — 7% — chance of developing breast cancer. However, though the data has been consistent across the different studies, the results don’t point to birth control pills as the specific reason for the higher risk. This means there may be another reason for the increased risk among women who take a birth control pill.

“I wouldn’t say every woman should be alarmed by this and immediately stop taking birth control pills,” says Dr. Barry. “It really depends on each woman and her needs for taking birth control pills as well as her other risk factors for getting breast cancer.”

Interestingly, these studies have also shown that women taking birth control pills may have a lower risk of developing endometrial, ovarian and colorectal cancers. Researchers believe that birth control pills reduce the number of times a woman ovulates, thereby exposing her less to hormones that can cause ovarian cancer. But further examination is needed for a definitive answer, Dr. Barry says.

Once a woman passes her childbearing years, it’s important she talks with her doctor about the necessity of continuing birth control so as not to increase her risk of breast cancer.

Reasons for taking the pill

“There are various reasons as to why a woman takes birth control pills, whether it may be to reduce menstrual pain, prevent pregnancy or ease symptoms from endometriosis, a condition that occurs when tissue that’s similar to the uterus’ lining grows outside the uterus,” says Dr. Barry.

She adds that all the reasons are personal. Additionally, other controllable factors can increase breast cancer risk, such as being overweight or drinking alcohol.

“Ultimately, breast cancer is one of the commonly diagnosed cancers among women, so every woman — whether they take birth control pills or not — should be educated about regular screenings and consult with her doctor to examine her risk,” says Dr. Barry.

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