So they did a comparison study with women who had a miscarriage?
I don’t believe in abortion at all, but this sounds like a stretch to me.
After conception, estrogen allows the body to maintain a pregnancy. Low estrogen causes miscarriages. Women getting abortions don't have low estrogen and thus the breast cancer connection.
They have, but the link is not as strong with miscarriages; abortion really raises the risk.
Personal Observation: Every woman I know who has had breast cancer, also had either an abortion or multiple miscarriages when they were younger. (A sample of 5)