Females who use hormonal contraceptives such as birth control pills have a higher risk profile for developing breast cancer, according to an Oct. 30 peer-reviewed study published in JAMA Oncology.

The study examined data from 2,095,130 females in Sweden between the ages of 13 and 49 from 2006, who were followed up until the end of 2019. Individuals with prior cancers of the breast, ovaries, uterus, and cervix, as well as those who received infertility treatment or ovary removal surgeries, were excluded from the study.

Between 2006 and 2019, researchers identified a total of 16,385 breast cancer incidents. Among study participants, 1.28 million females used hormonal contraceptives, contributing to 8,485 breast cancer cases. Among those who never used such contraceptives, there were 7,900 cancer cases.

The use of any type of hormonal contraceptive was associated with a higher risk of breast cancer, translating into one extra case per 7,752 users per year.

Hormonal contraceptives can either be progestin-only formulations or combined estrogen-progestin ones. Progestin is a synthetic form of the reproductive hormone progesterone found in the human body.

The study discovered there was a “statistically significant greater risk” of breast cancer from progestin-only contraceptives compared to combined formulations.

“This translated to 1 additional breast cancer case per 8572 users of progestin-only contraceptives compared to 14,417 for combined products,” it said.

Researchers analyzed six types of progestin used in hormonal contraceptives. It found that contraceptives with desogestrel and etonogestrel, the active metabolite of desogestrel, were associated with a higher risk of breast cancer than products containing levonorgestrel.

Despite having many users, contraceptives such as etonogestrel vaginal rings, medroxyprogesterone acetate injection, and combined oral drospirenone were found to have “no statistically significant increased risk” of breast cancer, according to the study.

“The finding that desogestrel may increase breast cancer risk more than other progestins is a novel finding that, to our knowledge, has not been previously reported,” researchers wrote.

The study was conducted by researchers from Uppsala University in Sweden.

However, in recent times, progestin-only contraceptives are increasingly popular, making a study on their long-term health impacts important, it said.

The study was funded by the Swedish Cancer Society, the Swedish Research Council, and the Sjöberg Foundation. The authors reported no conflicts of interest.

The CDC estimated that 54.3 percent of females aged 15 to 49 used contraception in 2022–23, with oral contraceptive pills being used by 11.4 percent of this group.

Breast cancer accounts for roughly 30 percent of all new female cancers in the United States annually, ACS said. In 2025, an estimated 316,950 new cases of invasive breast cancer are expected to be diagnosed among women.