Thorough examinations are discouraged in the UK
Women remain confused about the right way to check their breasts for early signs of cancer, says a charity.
Experts say there is no evidence that rigorous monthly "self-examination" reduces breast cancer deaths and it can lead to unnecessary biopsies.
In the UK, the focus is on breast "awareness", rather than more complex and involved checks.
However, Breast Cancer Breakthrough says some UK women rely on US-based websites recommending self-examination.
The Department of Health has not endorsed breast self-examination since the early 1990s, but US authorities still do.
Women who follow the programme often closely check their breasts on the same day in each monthly cycle, feel them using a certain pressure, in a standing and lying position, and can view them from different profiles using a mirror.
They are told to write down details of anything they find in a diary.
The Cochrane review looked at all the available evidence on the success of self-examination programmes, principally two large studies of a total of 388,535 women in Russia and China, half of whom self-examined, while the other half did not.
The death rates from breast cancer were the same in both groups, while there were almost twice the number of biopsy operations - used to take a tissue sample for analysis - in the self-examination group.
This, said the researchers, suggested that self-examination could be leading to more women receiving unnecessary biopsies.
"At present, screening by breast self-examination or physical examination cannot be recommended," they wrote.
'Unaware of advice'
Despite recommendations against self-examination in the UK, charity Breakthrough Breast Cancer said there were still likely to be many women who believed this was the right way to check their breasts.
Dr Sara Cant said: "There is a lot of information out there from the US, and this is easily obtained on the internet - and there are UK sites where this advice is given, usually with the best of intentions.
"On top of this, some women who started examining their breasts this way before the advice changed in the 1990s may be unaware that new advice has been issued."
She said that the best way for a woman to check her breasts was not to follow a strict examination routine, but to get to know what is normal for her, and feel them regularly for signs of any changes.
"We call it TLC - touch, look and check. This approach, coupled with regularly attending breast screening when invited, and modern treatments, has significantly reduced breast cancer mortality."
A Department of Health spokesperson said: "The Department of Health's policy on breast awareness, which has strong support from the nursing and medical professions, encourages women to check their breasts for what is normal for them but does not recommend routine self examination to a set technique.
"There is no scientific evidence to show that a formally taught, ritual self examination, performed at the same time each month, reduces the death rate from breast cancer or is more effective than a more relaxed breast awareness."