A study published in the European Journal of Gynecology and Oncology found women who gave first birth at 25 years of age or younger and had three or more pregnancies were at 50 percent reduced risk of breast cancer, compared with those nulliparous women.

Kabat G.C. from Albert Eistein College of Medicine in Bronx, New York discovered this association after they analysed data from 661 cases of breast cancer and 696 controls who received biopsy to determine whether they suffered benign breast disease.

A proposed hypothesis explains that a full-term pregnancy can mature the breast.  Early maturity of the female reproductive organ can make them less vulnerable to the effect of carcinogens.

Another case-control study led by Hadjisavvas A at The Cyprus Institute of Neurology and Genetics in Nicosia, Cyprus and colleagues found women with late menarche defined as after the age of 15 years were 46 percent less likely to develop breast cancer than women experiencing menarche at the age of 12 or earlier.

The study also showed that women who breastfed were 26 percent less likely than those who did not to develop breast cancer.

Women who have early menarche often have a longer child-bearing period, during which they have longer exposure to high levels of estrogen, which promotes the growth of breast cancer cells. 

The findings were published in the Aug 2010 issue of BMC Cancer.

Breast cancer is expected to be diagnosed in more than 200,000 men and women and kill about 50,000 in 2010 in the United States, according to health organizations.  One in eight women will be diagnosed with the disease in their lifetime.

More reports will be published here in the National Breast Cancer Awareness Month to help readers better understand the disease and how to reduce the risk.

Jimmy Downs and editing by Rachel Stockton