Women who have used birth control pills in the past apparently have no increased risk for heart disease, according to a new study that provides the most conclusive evidence on the question yet.

"It's reassuring," said Dr. Louis Tyrer of the Planned Parenthood Federation of America of the study published Wednesday in The New England Journal of Medicine.Doctors were concerned past use of oral contraceptives might increase the risk for heart disease because the pills tend to increase blood pressure and blood clotting and cause possibly unhealthy changes in blood fat levels.