Commonly used injectable contraceptives influence the risk of developing several types of cancer, a joint ANU/National Health Laboratory Service (South Africa) study has found.
The study builds on previous research that showed women using oral contraception have a temporarily increased risk of breast cancer and cervical cancer and a decreased risk of ovarian cancer and cancer of the lining of the womb.
The researchers found that South African women who had recently used one or both of these contraception methods were about 1.7 times more likely to develop breast cancer and 1.4 times more likely to develop cervical cancer than women who had never used hormonal contraception.
However, this increased risk disappeared within a few years after women stopped taking the contraception.
The study also supports previous findings that extended use of hormonal contraception is associated with a reduced risk of ovarian cancer and cancer of the lining of the womb.
The paper is published today in PLoS Medicine.