Had 1st child at 21, 2nd at 30. does this lower my risk for breast ca? if so, how much approx? 33 y/o female, first menses at 11 y/o. no 1st deg hist.

Pregnancy, Breast CA: According to a collaborative int'l study, conducted in 7 diff parts of the world, it is estimated that women having their first child when aged under 18 years have only about one-third the breast cancer risk of those whose first birth is delayed until the age of 35 years or more. Births after the first, even if they occur at an early age, have no, or very little, protective effect.

Doubt it: While it is said that women who have never had children have a higher incidence of breast cancer, I suspect that it is mostly environmental and that exposure to certain carcinogenic substances or to the MMTV virus increase the likelihood of developing breast cancer. It is now shown that endogenious DNA viral sequences for breast cancer can be passed down genetically.