Kathy OsbornDid you have a baby right after college, or did you wait until your late 30s? Did you breast-feed or use bottles? Believe it or not, though the connections aren't yet completely understood, these and other details may influence your chances of developing breast cancer.
You may have a decreased risk if…
. You've given birth at least once. In fact, research suggests that each time you deliver, you reduce your chances of developing breast cancer by about 7 percent.
. You've breast-fed. This benefit appears to be especially big for women with a family history of cancer: One study found that those who nursed were 59 percent less likely to develop premenopausal breast cancer than women who didn't nurse.
. You had your first baby early in life. The younger a woman is when she delivers her first child, the lower her risk of breast cancer down the road appears to be.
. You had preeclampsia during a pregnancy. Surprised? Researchers are investigating ways in which certain chemicals released by the placentas of women who have preeclampsia may actually inhibit the growth of breast cancer cells.
You may have an increased risk if…
. You've never been pregnant. In that case, you've had more menstrual cycles and have been exposed to more estrogen over the course of your lifetime than a woman who's given birth, possibly raising your cancer risk. One theory suggests that the breast cells of women who've never been pregnant may be particularly vulnerable to the effects of that hormone.
. You started your family later in life. A woman who has her first pregnancy after age 35 may have an increased risk of breast cancer, compared with one who had her first child at a younger age.
. You delivered a high-birth-weight baby. Research indicates that breast cancer risk may increase by 16 percent with each kilogram increase (about 2.2 pounds) in your baby's weight. Some research suggests that's because heavier babies' bigger placentas produce more hormones to which mothers are then exposed, increasing their odds of cancer.