Breast implants may make it harder for doctors to interpret mammograms, research finds.
Implants may make scans less clear
However, scientists found no evidence that the problems led to cancer reaching a more advanced stage before it was picked up.
Neither did breast augmentation appear to increase the risk of developing breast cancer.
The research, by Seattle's Group Health Cooperative is published in the Journal of the American Medical Association.
The researchers found that, among women who had not had breast implants, mammograms accurately raised concerns in 66.8% of women who went on to be diagnosed with breast cancer in the next 12 months.
The figure among women who had undergone breast augmentation was only 45%.
The problem with breast implants is that they show up as a solid white mass on the mammography film, blocking the view of the breast tissue.
Even when mammography technologists use a special technique called implant displacement views, which attempts to move the implant out of the way, there is still breast tissue that cannot be seen on the mammogram.
Scans can pick up signs of cancer
But although mammography does not find cancer as well in women with implants, this does not seem to result in more advanced cancers at diagnosis.
The study found that women with implants were diagnosed with cancers of similar stage and size as women without implants.
The reason why this should be so is not clear. However, the researchers suggest it may be easier for women with implants to detect cancers missed by mammography because they often have less of their own breast tissue.
Alternatively, tumours may be more noticeable because the implant provides a firm platform to press against.
In addition, women with breast implants are told to check their breasts often for any problems with the implant, so they may be more likely to find lumps on their own.
Finally, women with implants may be more body conscious and seek medical advice more quickly if they have a symptom.
The researchers say that women who have undergone breast augmentation should be screened at the same regular intervals as others, but they should be more ready to question the result if they feel they have suspicious symptoms.
Samia al Qadhi, of the charity Breast Cancer Care, said: "We know, from earlier studies, that mammography may be less effective in women who have silicon implants because they obscure a large proportion of the breast.
"We also know that calcium salt deposits around implants may also interfere with standard mammography used to detect breast cancer.
"Breast Cancer Care advises women to make the radiographer aware they have implants so that the screening technique may be adapted to show as much breast tissue as possible on the x-ray."
Dr Richard Sullivan, of the charity Cancer Research UK, told BBC News Online: "This isn't an unexpected finding, as we know mammography can be difficult in women with very dense breast tissue.
"The study doesn't provide any evidence that women with implants are more likely to present with advanced disease, but even so, future developments in breast augmentation need to take into account the possible impact on screening."