Abortion does not raise breast cancer risk

Abortion and miscarriage do not raise the risk of breast cancer, according to a study published Monday by the US National Cancer Institute in the Archives of Internal Medicine.

The 10-year study, performed on a sample of 105,716 US participants, rejects prior studies that suggested a link between prematurely terminated pregnancies and breast cancer.

The subjects were nurses aged 29-46 at the start of the study. They answered questions every two years via anonymous questionnaire about their medical history, including whether they had abortions, miscarriages and breast cancer.
"Among this predominantly pre-menopausal population, neither induced nor spontaneous abortion was associated with the incidence of breast cancer," said the study's authors from Brigham and Women's hospital and Harvard Medical School in the northeastern state of Massachusetts.

The data provides "further evidence of a lack of an important overall association between induced or spontaneous abortions and risk of breast cancer."

"We found no association between induced abortion and breast cancer incidence and a suggestion of an inverse association between spontaneous abortion (miscarriage) and breast cancer during 10 years of follow up," the study said.

However, the inverse relationship -- women who had a miscarriage before age 20 showed a reduced risk of breast cancer -- was found in a small sampling of women and "thus, chance has to be considered as a possible explanation."

The conclusions of the study were similar to those of a 2003 panel convened by the National Cancer Institute which found no evidence linking abortion or miscarriage to higher breast cancer rates.