Study: Breast Cancer Risk Tied to Multiple Childbirth in Black Women

African-American women who give birth to at least four children have an increased risk of breast cancer at a young age, but a lower risk after age 45, according to Boston University researchers.

In following more than 50,000 women enrolled in the Black Women’s Health Study, the researchers found that the risk of breast cancer before age 45 was more than double among women with at least four children compared to those with a single child.

But they reported in the Journal of the National Cancer Institute that these same women were only half as likely to develop breast cancer after age 45 compared to those who had given birth only once.

The researchers noted that breast cancer incidence is higher among African-American women than among white women before age 45 but lower at older ages, and said their findings may help explain these "puzzling differences."

And since breast cancer is generally more common at older ages, the researchers said having a larger family appears overall to decrease rather than increase a black woman's risk.

Other sources: Journal of the National Cancer Institute