Breast Cancer and Birth Weight Breast cancer is one of the leading causes of death for women, so researchers are constantly on the lookout for possible causes and contributing factors. There are some well-established risk factors like a family history of breast cancer. The connection between infant weight and risk of breast cancer has been studied before, but this is the first time birth weight has been reported as an individual risk factor independent of other factors. Research was completed at the Medical Branch of the University of Texas.

The study examined information from previously completed studies – so there was no new information collected, just a gathering of information already collected. The data included information on pregnancy hormones, known breast cancer risk factors, maternal birth weight, infant weight and diagnosis of breast cancer.

Information collected revealed that women with infants weighing in excess of 8.25 pounds had additional risk factors for breast cancer later in life. Researchers believe the connection has something to do with high estrogen levels and low levels of anti-estrogen. The presence of growth factors that work like insulin could also play a part. Together these factors create an environment that is optimal for breast cancer development and growth.

Researchers and doctors noted that women cannot change hormone expression during pregnancy, but women can adopt healthy lifestyle habits that reduce the risk of breast cancer to help combat the risk. For instance, eating a healthy, whole food diet and making a concerted effort to exercise everyday can reduce a woman’s risk of breast cancer.

The connection between infant weight and increased risk factors for breast cancer is not completely clear, but researchers believe it has something to do with stem cells in the breast. The cells are part of breast cancer development and growth and they may have a memory, of sorts, of the hormones expressed during pregnancy. If the stem cells remember the optimal environment for breast cancer growth – due to high estrogen and low anti-estrogen, they may use that memory later when breast cancer develops. This theory is based on animal studies on breast cancer.

Researchers plan on continuing the study of birth weight effects on breast cancer risk and development. In future studies they plan on investigating whether or not the weight of your infant(s) can be used as a predicting factor for breast cancer development.

Source: University of Texas Medical Branch at Galveston. July 18, 2012.