This belief is based upon particular risk factors for breast cancer, which are said to be more prevalent in lesbians such as smoking and poor diet; and upon differences in preventive health behaviours: in particular, lesbians are said to be less likely to practise breast self-examination. It has also been suggested that lesbians are at greater risk because they are less likely to be pregnant; they therefore do not stop producing oestrogen at any stage. It is thought that this might increase risk of breast cancer.
It is also felt by some health care professionals that lesbians do not require cervical smear tests. This is because it is assumed that cervical cancer is caused by exposure of the cervix to sperm. Research suggests however, that there are other causes of cervical cancer, including HPV, sexual behaviour (including having unprotected sex at a young age – some lesbians may have done this), smoking, and diet. Research suggests that some lesbians have had sex with men in the past, lesbians are more likely to smoke, and likely to smoke more than heterosexual women, and have a poor diet. Research therefore indicates that all women with a cervix should receive cervical screening.