A mammogram is a type of x-ray that is used to detect early changes in breast tissue which may possibly be cancerous.
In Australia, breast screening programmes recommend that all women over the age of 50 have a mammogram every two years. Women can choose to have mammography from as early as 40 years of age.
Mammography in the age group between 40 and 50 may be done in combination with an ultrasound scan of the breast.
A mammogram done before the age of 40 is not as reliable at picking up lesions as the breast tissue is usually more dense and difficult to differentiate from any lesions.
I believe all women should be encouraged to have their mammography done every two years from the age of 40 years onwards as this technique can potentially pick up a very early lesion, even prior to the time when it may be detected by feel.