The California State Legislature passed a bill last Friday requiring doctors to inform women if they have dense breasts after a mammogram, making California the second state this summer and the third state so far to have passed a so-called breast density law.

The bill, SB 791, passed the state Senate 35-1, and is now going before Gov. Jerry Brown to get signed.

When he signs it, starting next year, Calif. radiologists will have to send women with dense breasts, as determined by an American College of Radiology-developed system, this text:

Because your mammogram demonstrates that you have dense breast tissue, which could hide small abnormalities, you might benefit from supplementary screening tests, depending on your individual risk factors. A report of your mammography results, which contains information about your breast density, has been sent to your physician's office and you should contact your physician if you have any questions or concerns about this notice.

Texas Gov. and Republican presidential hopeful Rick Perry signed into law a similar bill, Texas Act HB 2102, or Henda's Law, in June. And breast density legislation was also passed in Connecticut in 2009.

New Hampshire, Massachusetts, New York and Florida all have similar legislation pending.

The American College of Radiology Imaging Network says that around 40 percent of women getting screening mammograms have dense breasts, with younger women typically having denser breasts.

Dense breasts are less fatty, with more connective tissue. The connective tissue appears white on a mammogram, just like the cancer, making it harder to diagnose, according to Are You Dense, an advocacy group.

A January 2011 study by the Mayo Clinic found three-quarters of cancers in women with dense breasts are missed by mammograms.

"When it comes to your health, ignorance is not bliss. What you don’t know can hurt you,” State Sen. Joe Simitian, a Democrat from Palo Alto who authored the bill, said in a statement.

The idea for the bill came from by Amy Colton, a registered nurse who had breast cancer not discovered by a mammogram, and who learned she had dense breasts only after her cancer was diagnosed, according to Are You Dense. She suggested the bill in Simitian's "There Oughta Be a Law" contest.

However, the bill met some opposition from the California Medical Association. Writing about an earlier incarnation of the bill, SB 173, the CMA warned that it could bring legal and practical problems for Calif. doctors.

"Because the scope of who must receive the notice is so broad, women will be ‘scared’ into thinking they need these expensive additional screenings when it isn’t at all warranted, leading to increased costs and pressures on a physician’s practice," the group wrote in a notice on its website. "Moreover, because the grading of the condition that may/may not lead to their receipt of the prescribed notice is subjective in nature, the absence of the notice could lead to lawsuits against doctors if a patient is later diagnosed with breast cancer."

But the bill was backed by several other groups, including the California Nurses Association, the Breast Cancer Fund, the California Association of Health Underwriters and California NOW.

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