Can having a baby or two help me prevent breast cancer?

Yes: Yes . Woman by having children, and by breast feeding them will have lesser incidence of breast cancer, than the woman that did not.

Yes.: Women with late menarche, early menopause, and first full term pregnancy by 18 have a significantly reduced risk.

Weigh the risks: Even if "having a baby or two" were to reduce your risk of breast cancer, there are risk associated with child bearing. You ought to consult your doctor to weigh the relative risks and benefits of your proposed actions. Some might argue that bringing babies into this world for "reducing" your risk of breast cancer is not ethical.