i read a study that said that breast feeding could possibly reduce the occurences of breast cancer, and this could be why it occurs less frequently in less developed countries, because they are generally having more children, and they breast feed them instead of using formula.
Over 500 years ago, what passed for scientists back then, used to call breast cancer the nuns disease, because only nuns got it. There is a definite link between breast cancer and not nursing children. Abortion comes into play because you can't nurse an aborted child.
Actually, it's just the opposite: one of the problems for health-care workers in undeveloped countries is to persuade women to breast-feed their children. They tend to want to give formula as being somehow more modern or healthier, when in fact formula is nowhere near as good for babies, doesn't provide the immune protection of breast milk, and often has to be prepared with water that's less than clean and/or put into bottles that aren't sterile. So to reduce the incidence of fatal infant diarrhea, health workers try to talk poor women into saving their resources to feed themselves better and giving breast milk to their babies.
Breast feeding makes a huge difference. For every year of nursing, it cuts your risk by 50%! It makes sense, as the breasts were doing what they were designed to do. As an interesting side note- nuns are known to have a higher rate of all female cancers, once presumes b/c they are not having babies.