Dec. 12 (UPI) -- Women who recently gave birth have an 80 percent higher risk of developing breast cancer than women in the same age group who haven't, according to a recent study.
Research published in the Annals of Internal Medicine analyzed nearly 900,000 women age 55 and younger from 15 studies around the world and found that women with an elevated risk of breast cancer also had a family history of the condition and a greater number of prior births.
"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," Hazel B. Nichols, an assistant professor in the University of North Carolina School of Global Public Health and study author, said a news release. "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."
Women who had their first child after age 35 had a higher risk for breast cancer than women who first gave birth before age 25.
While 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.
"We need to recognize that the traditional risk factors for breast cancer do not always operate the same way at younger ages," Nichols said.
In later years, the risk of breast cancer in the group was low, with 41 more cases of breast cancer diagnosed in every 100,000 women who gave birth between ages 41 and 45 birth. And the risk increased with age, as there were 247 more cases per 100,000 for women who gave birth at age 50.
"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.