When should women start getting routine mammograms: In their 40s, 50s or 60s?

If you're not sure, you're not alone.

A new study of nearly 90,000 women suggests the screening test has little impact on breast cancer death rates among women between the ages of 40 and 59 - a controversial finding that challenges current recommendations and common practice in the U.S.

Should You Get a Mammogram?

A mammogram is an X-ray of the breast used to detect non-palpable tumors. The U.S. Preventive Services Task Force recommends biennial mammography starting at age 50. But advocacy groups like BreastCancer.org and the American Cancer Society recommend annual mammograms starting at age 40.

Bottom line: it's confusing.

So what's the risk of having too many mammograms? According to the new study: unnecessary treatments. One in five cancers detected during the 25-year study was "over-diagnosed," meaning women underwent treatment for tumors that might never have affected their health.

Breast Cancer Screening May Cause More Harm Than Good, Study Finds

It's estimated that for one woman's life to be saved by a mammogram, 2,000 women would have to be screened leading to 200 anxiety-provoking false positives and 10 unnecessary surgeries. The X-ray also exposes women to small doses of radiation.

But forgoing mammograms can also be risky, according to a 2013 study that found seven out of 10 women who died from breast cancer had never had the test. Half of them were younger than 50.

Mammograms Before 50 Could Save Lives, Researchers Say

So what should women take away from the debate? Breast cancer screening is important, but mammography isn't the only tool. A clinical breast exam performed by a skilled doctor or nurse can flag suspicious lumps for more sensitive follow-up tests, and knowing your own breasts can help you spot changes early and get them checked out.

Find out more about breast cancer screening.

This year alone more than 230,000 American women will be diagnosed with breast cancer, and 40,000 will die from the disease, according to the American Cancer Society. Talk to your doctor about the benefits and risks of mammography.

A new study has revived an old debate about when women should start getting mammograms. (Image credit: Getty Images)