However since it is socialized medicine in Denmark, they keep records on every patient. They know who has had an abortion and who has had breast cancer. It is all in the records there. They don't have to interview the patient and therefore there will be no "recall bias."
This "cohort" study was of 1.5 million women. It was a significant study. Since the records were already kept by the time of the study, there was no way the doctors could have known in advance for 60 years to "lie" into records so as to bias this future study.
In fact, no cohort study has ever found a link between abortion and breast cancer. Only the methodology flawed "case-control" studies have found such a link, and it has been shown that this is solely due to recall-bias -- where healthy women underreport their abortion histories as compared to women who know they have breast cancer.
If you really wanted to know you would read these studies and counter research papers and not take the word of only those that have a one desired outcome (I believe at least one was published in the New England Journal of Medicine.) The counter research has been peer reviewed and yes, there is disagreement on both side of the debate. Anyone who says it is conclusive is lying through their teeth. I am not a scientist but the case made against the Denmark study sounds pretty darn good to me.
All that aside, I am against the killing of innocent humans. Any doctor will tell you that scientifically the fetus is all human and separate from the mother before they even know they are pregnant. It is not a tumor nor a abnormal growth. It is a person and the only way to justify killing it is to know when and if a soul enters the body making it a sentient being or some other provable and great enough separation from the basic human race. Since that cannot be proven it is always wrong to kill a child.
Would we kill any other segment of the population only to benefit another segment with no extreme circumstances (most abortions are not preformed to save a mothers life (2%? I might be wrong) they are preformed because the mother does not want the baby for some reason or another)?
Would you say it is okay to kill selected old people? Many would benefit from this. If not, why and what is the differance?