What epidemiological research has been conducted showing that abortion increases breast cancer risk?
Opponents of the abortion-breast cancer link do not challenge the biological reason for the link. They challenge the evidence showing a statistical correlation – the epidemiological research. Epidemiology is the study of disease trends in large populations. By itself, epidemiology cannot establish whether or not a cause-effect relationship exists, but it can be used as one more piece in the puzzle that supports a cause-effect relationship. Seventy epidemiological studies have been conducted in Asia, Europe, Australia and the U.S. since 1957. Eighty percent of these studies report risk increases for women who had abortions. The National Cancer Institute specifically commissioned a study by Janet Daling and her colleagues. She reported that, Among women who had been pregnant at least once, the risk of breast cancer in those who had experienced an induced abortion was 50% higher than among other women. Highest risks (more than double) were observed when the abortion was done at ages young
