Research has shown that breast cancer risk is lower in women who are younger than 25 when they have their first child. Research has also shown that breast cancer risk is lower in women whose periods started at an older than average age.
Instead of looking at age, a study looked at the length of time between when a woman started having periods and when her first child was born. The study showed that the more time between the two events, the higher the risk of breast cancer.
Women who had their first child 16 or more years after their first period were 1.5 times more likely to be diagnosed with breast cancer than those who had their first child less than 5 years after their first period. The researchers aren't sure why this happened, but they think that hormones might play a role.
A woman's age when she started having periods didn't affect breast cancer risk in this study.
Other research has shown that women who breast feed have a lower risk of breast cancer, no matter how old they were when they had their first child.
For both personal and practical reasons, having a first child when a woman is 25 or older is common in the United States. Concerns about the increased breast cancer risk associated with that timing may be outweighed by these personal and practical reasons. And it's also important to remember that there are many other lifestyle choices that can influence breast cancer risk and overall health. To learn more, visit the breastcancer.org Lower Your Risk section.