"What most people know is that women who have children tend to have lower breast cancer risk than women who have not had children, but that really comes from what breast cancer looks like for women in their 60s and beyond," coauthor Hazel Nichols said in a statement. "We found that it can take more than 20 years for childbirth to become protective for breast cancer, and that before that, breast cancer risk was higher in women who had recently had a child."
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Despite their findings, the scientists noted overall risk of breast cancer is still low for mothers after pregnancy. They also discovered their results didn’t apply to all younger women. Risk was higher for women who had their first child after 35, but there was no increased risk of breast cancer after a recent birth for women who had their first child before 25.
“This is evidence of the fact that just as breast cancer risk factors for young women can differ from risk factors in older women, there are different types of breast cancer, and the risk factors for developing one type versus another can differ,” Nichols said.
The authors now hope their investigations will help improve prediction of breast cancer and lead to greater awareness among young mothers.
“There are many ongoing studies that are trying to improve our ability to do breast cancer risk prediction on the individual level,” Nichols concluded. “This is one piece of evidence that can be considered for building new prediction models.”
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