Some of those studies had suggested a possible connection, but the authors of the report published in The Lancet medical journal said that was the result of an error in methodology.
"We hope that this research will put a stop, once and for all, to the persistent claims that abortion is a risk factor for the disease and help give reassurance to women," said Delyth Morgan, chief executive of Breatkthrough Breast Cancer, a British breast cancer research organization which was not involved in The Lancet report.
The possible connection between abortion and breast cancer has been controversial in the United States, where opponents of abortion and some members of Congress had raised the issue.
A few studies in the early 1990s suggested a possible link. But the U.S. National Cancer Institute last year concluded that those studies were flawed, and that no study undertaken since 1995 had suggested any connection.
The study published in The Lancet was done by the Collaborative Group on Hormonal Factors in Breast Cancer, based at Oxford University, which analyzed data from 53 epidemiological studies from 16 countries.
The studies included data from 44,000 women who had disclosed an abortion or miscarriage before they were diagnosed with breast cancer, and from 39,000 women who were interviewed after they were diagnosed with breast cancer.
Among the 44,000 women, researchers found no link between breast cancer and an earlier abortion or miscarriage.
The results of the studies based on the 39,000 post-diagnosis interviews were unreliable because of the risk of "falsely positive association between the risk of breast cancer and a retrospectively reported history of induced abortion," the report said.
"The totality of the worldwide epidemiological evidence indicates that pregnancies ended by induced abortion do not have adverse effects on women's subsequent risk of developing breast cancer," said Professor Valerie Beral, an epidemiologist who was one of the study's authors.