Breast compression may cause some discomfort for a brief time during each x-ray, but it should not be painful. Breast compression helps obtain better images by:
Spreading out the breast so the maximum amount of tissue can be examined.
Allowing a lower x-ray dose to be used, since the x-ray beams pass through a thinner amount of tissue.
Holding the breast in place to prevent blurring caused by motion.
If you have sensitive breasts, schedule your mammogram at a time of the month when your breasts will be less tender. In general, the week after a period is when breasts are less tende.