(CNN)All hormone contraceptives, including progestagen-only "minipills," carry a small "excess risk" of breast cancer, according to a new study by researchers at the University of Oxford, but the overall risk remains low.
The study, published Tuesday in the journal PLOS Medicine, bridges a research gap by investigating the link between breast cancer and progestagen-only contraceptives.
"Use of combined oral contraceptives, containing both estrogen and progestagen, has previously been associated with a small increase in breast cancer risk but there is limited data about the effect of progestagen-only hormonal contraceptives," the authors wrote.
The study found that progestagen-only contraceptives are associated with a 20% to 30% relative risk for breast cancer, which aligns with previous research on combined hormone contraceptives. The overall risk of breast cancer among hormone contraceptive users is low, especially for younger women, and past studies have shown that the excess risk is gone entirely about 10 years after stopping.
The study does not indicate that hormonal contraceptives cause breast cancer but rather investigated potential links to the disease.
What are progestagen-only contraceptives?
Progestagens, or progestin, are a type of synthetic hormone drug that mimic the natural hormone progesterone, which is crucial for menstruation and pregnancy.
Unlike combined hormone contraceptives, progestagen-only contraceptives do not have estrogen. Types of progestagen-only contraceptives available in the UK and US include the implant, the hormonal intrauterine device (IUD), the contraceptive injection and the minipill.
In the UK, which is ranked highest for access to contraception on the 2023 Europe Contraception Policy Atlas, prescriptions for progestagen-only contraceptives are almost as high as for combined oral contraceptives.
In the US, the combined pill is the most popular hormonal contraception, but a significant percentage of women are choosing an implant or IUD, according to the US Centers for Disease Control and Prevention.
Progestagen-only contraceptives work to prevent pregnancy by thickening mucus in the cervix to stop sperm reaching an egg and, in some cases, can stop ovulation completely.
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