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New research details the breast cancer risk from progestin-only contraceptives. Mindful Media/Getty Images
  • Past research has shown that hormonal contraceptives containing both estrogen and progestin are linked to a slight increase in breast cancer risk.
  • Now, a new study reports that progestin-only birth control has a similar breast cancer risk.
  • Experts, however, say the overall risk from both types of birth control remain relatively low.

Progestin-only and progestin with estrogen contraceptives are associated with a slight increase in breast cancer risk, according to a study published today in the open-access journal PLOS Medicine.

Previously, hormonal contraceptives containing both estrogen and progestin were associated with a slight increase in breast cancer. Combination contraceptives come in various forms including oral pills, patches, and vaginal rings.

However, researchers in the new study report that progestin-only birth control also increases the risk of developing breast cancer, regardless of the form of contraceptive. Examples of progestin-only contraceptives include oral pills, patches, injectables, and intrauterine devices (IUDs).

Scientists from the United Kingdom used the Clinical Practical Research Datalink for their study.

They evaluated the medical records of 9,498 women under 50 with invasive breast cancer. All the women received their diagnosis between 1996 and 2017.

The researchers also looked at 18,171 medical records to use as a control group.

The findings included:

  • 44% of women with breast cancer had hormonal birth control prescriptions, with about one-half for progestin only.
  • 39% of the women in the control group had a prescription for hormonal birth control; again, about one-half were for progestin only.
  • The estimated 15-year absolute excess risk associated with 5 years of hormonal contraceptive use was 8 per 100,000 women ages 16 to 20 and 265 per 100,000 women ages 35 to 39.

The risk of breast cancer was similar regardless of whether birth control was progestin and estrogen combined or progestin only.

“We have known that oral contraceptives slightly increase the risk of breast cancer,” said Dr. Parvin Peddi, a medical oncologist and director of Breast Medical Oncology for the Margie Petersen Breast Center at Providence Saint John’s Health Center and Associate Professor of Medical Oncology at Saint John’s Cancer Institute in California.

“This study aims to determine if progestin only containing oral contraceptives has a lower risk or whether the delivery mode, for example, oral vs. injectable vs. intrauterine device, affects risk. The study found a similar increased risk of breast cancer among all the above options,” Peddi told Healthline.

“The main take-home message is that this study finds that women do not need to choose a progestin-only containing birth control medication because of the perceived lower risk of birth cancer,” she added.

“On the other hand, it’s important to note that the absolute increased risk of breast cancer from any of these medications is quite low, and this study should not dissuade women from using hormone-containing birth controls,” Peddi said. “The risk of breast cancer was seen in less than 0.5% of women aged 35-39 due to these medications and in even fewer women who used these medications at a younger age.”

Despite the potential risk, there are benefits to using hormonal birth control methods.

“The study does not mention what we have known from combined estrogen/progestin pills for many years; breast cancer tends to be less spread at the time of diagnosis,” said Dr. Monte Swarup, an OB/GYN in Chandler, Arizona, and founder of the HPV information site HPV HUB.

Hormonal birth control might also help with the early detection of cancer.

“Some breast cancers are estrogen or progestin positive and some are not,” Swarup told Healthline. “So, the study makes sense that the hormones could stimulate existing cancer, so it is detectable earlier by physical exam or mammogram.”

There are many different methods of birth control – from abstinence to surgical methods that prevent pregnancy permanently.

Experts say women should choose a birth control method that aligns with their beliefs and lifestyle.

According to the Office of Disease Prevention and Health Promotion, birth control methods include:

  • Abstinence
  • Fertility awareness methods work best for women who have regular cycles. After learning about their body and which days they are most likely to get pregnant, they can avoid having sex. This method is not as effective as IUDs and hormonal methods.
  • Barrier methods include male and female condoms, diaphragm, cervical cap, sponge, and spermicide. They work by preventing the sperm from getting to the egg.
  • Copper intrauterine device (IUD). An IUD is a small T-shaped device that is placed inside the uterus by a medical professional. Made of copper, Paragard is a non-hormonal method used to prevent pregnancy for up to ten years.
  • Hormonal methods use estrogen, progesterone, or a combination of both. Different forms of hormonal birth control exist, such as an implant, shot, patch, ring, IUD, or birth control pills. Hormonal methods are prescribed by a medical professional.
  • Emergency contraception pills, such as Plan B, must be taken within five days of unprotected sex; the sooner you take them, the more effective they are. Some are available over-the-counter at a pharmacy.
  • Sterilization includes vasectomy for men or tubal ligation for women. It is considered a permanent solution. It can sometimes be possible to reverse sterilization, but it might not work.

Birth control is meant to prevent pregnancy. Other than male and female condoms, the methods do not reduce or prevent sexually transmitted infections (STIs).

The birth control pill is the most common form of birth control in the United States, according to the National Institutes of Health. About one-fourth of women between 15 and 44 who currently use contraception use the pill. Most use pills with estrogen and progestin combined.

“The primary use for progestin-only birth control methods is during breastfeeding as they do not diminish milk supply,” Swarup said. “Another benefit of this type of contraceptive is that it is useful for women who cannot take estrogen because of health conditions, such as a history of a blood clot.”

“This type is slightly lower in efficacy and can lead to irregular bleeding,” Swarup added. Determining the best birth control method is complicated and should be discussed with a medical professional. “There are many considerations based on the patient’s medical history, goals, and side effects.”