This conclusion is surprisingly opposite of the previous believe that women who have children tend to have a lower breast cancer risk than those who do not. The new findings, reported in the Annals of Internal Medicine, come from combining data from 15 studies of nearly 890,000 women of varying ages across three continents. The research group led by University of North Carolina Lineberger Comprehensive Cancer Center revealed instead that the “protection” from cancer can take more than 20 years after women give birth to take effect. By 34.5 years after birth of the youngest child, the breast cancer risk is 23 percent lower than the risk in women who had never been pregnant.
In women 55 years and younger, breast cancer risk was highest about five years after giving birth, according to the study, and the risk for those mothers was 80 percent higher than women who did not give birth. However, younger women are still less at risk for developing breast cancer than women over age 50. Researchers even determined no increased risk for women who had their first child before age 25. The findings “shouldn’t change women’s behavior with regard to when a woman decides to have a first child,” Mia Gaudet, scientific director for epidemiology research at the American Cancer Society, said. “It may perhaps change how and when a woman begins to be screened for breast cancer,” she added.