One of the world's largest studies of the contraceptive pill has found that women who have taken it can expect longer lives and are less likely to die from any cause, including cancer and heart disease.
British researchers said their study, which should reassure many millions of women across the world who have taken oral birth control pills, found no link between the drugs and an increased long-term risk of dying sooner.
"The results of this study are enormously reassuring and suggest that in the longer term the health benefits of the contraceptive pill outweigh any risks," said Richard Anderson of Edinburgh University and the Medical Research Council human reproductive sciences unit, who was not involved in the study.
The research, published in the British Medical Journal on Friday, followed 46,000 women for nearly 40 years, creating "more than a million woman-years" of observation, according to Philip Hannaford from Aberdeen University, who led the study.
The results showed that in the longer term, women who used oral contraception had a significantly lower rate of death from any cause, including heart disease and all cancers, compared with women who had never taken it.
But the scientists said their findings may only be true for women who have taken older-style pills rather than those on more modern types of drugs, since their study began in 1968.
"Many women, especially those who used the first generation of oral contraceptives many years ago, are likely to be reassured by our results," Hannaford and colleagues wrote.
Around 12 million women in the United States and some 3 million women in Britain take the contraceptive pill.
Earlier reports from the same study — known as the Royal College of General Practitioners' Oral Contraception Study and one of the world's largest ongoing investigations into the health effects of oral contraceptives — suggested the drugs may increase the risk of dying sooner, particularly in older women or those who smoked.
While the newest data also showed a slightly higher risk in women under 45 who are current or recent users of the pill, the researchers said the effects in younger women disappear after about 10 years and the benefits in older women outweigh the risks in younger women.