Do Larger Infants Raise Breast Cancer Risk?

Women who give birth to large infants may be 2.5 times more likely to develop breast cancer than women who give birth to the smallest babies.

The reason may be pregnancy hormones.

Researchers at the University of Texas Medical Branch at Galveston looked at data from two studies involving a total of more than 24,000 women. They found that women who gave birth to the largest babies - those in the top quintile - were more likely to have a high concentration of estriol, alpha-fetoprotein and plasma protein-A, all of which are present during pregnancy.

More hormones

The larger the infant, the higher the concentration of these hormones in the pregnant mother.

High levels of some of these hormones also encourage breast cancer to develop.

"Women can't alter their pregnancy hormones, but they can take steps to increase their general protection against breast cancer," says Radek Bukowski, M.D., the study's lead author.

Lowering the risk

He points to breastfeeding, having more than one child, healthy eating, and exercise as proven ways to lower the risk of getting breast cancer.

The study was published in the journal PLoS ONE. Although it found an association between hormone levels, infant birth weight, and breast cancer risk, researchers say more studies are needed to prove a cause-and-effect relationship.

Always talk with your health care provider to find out more information.