No smaller thing has ever made a bigger difference than the contraceptive pill. Licensed in the US in 1960, it was soon being taken by women round the world - solving an old problem and granting new freedom. Its continuing popularity looks assured this week, after an authoritative study suggested the balance of health pros and cons comes out on the positive side. More reliable than alternatives, the hormonal treatment gives couples more control over the timing and number of their children. A 1995 medical scare saw thousands of British women temporarily stop taking the pill, and the effects - 20,000 more pregnancies and 10,000 extra abortions - are a reminder of its power. The waves it created, however, cannot be gauged by demographic figures alone. In a song called The Pill, country dame Loretta Lynn welcomed an era where instead of endlessly breeding, women could finally escape the confines of the "brooder house". Big changes always encounter reaction, and it arrived with the Pope's 1968 anti-contraceptive encyclical; this week's study will encourage millions of women to continue ignoring its requirements. The risk of unwanted pregnancy had always saddled women with anxieties that did not weigh on men in the same way; those taking the pill could enter relationships on more equal terms than before. But true equality will arrive only when men take their full share of responsibility. Take-up of a new male pill, when it comes, will test whether that is finally happening.