More women are learning that their breasts are so dense that it's harder for mammograms to spot cancer. But new research suggests that automatically giving them an extra test isn't the solution.

Laws in 19 states require women to be told after a mammogram whether they have dense breasts. Similar legislation has been introduced in Congress.

What's not clear is what a woman who is told her breasts are dense should do next, if anything. Some of the laws suggest that extra screening may be in order.

Not so fast, scientists reported last week. They modeled what would happen if women with dense breasts routinely got an ultrasound exam after every mammogram, and calculated that such a policy would cost a lot, in extra tests and false alarms, for a small benefit.

For every 10,000 women who got supplemental screening between ages 50 and 74, three to four breast-cancer deaths could be prevented - but 3,500 cancer-free women would have needless biopsies, the study found. "There are people with dense breasts that are not at high risk," said study coauthor and physician Karla Kerlikowske of the University of California. More work is needed. - AP