The birth of a baby boy, created using sperm frozen for a world-record 21 years, offers new hope to thousands of young people who may lose their fertility after cancer treatment, doctors said. The child, born in 2002, could have been conceived in the year that Pol Pot's regime fell and Margaret Thatcher swept to power in Downing Street. But in 1979 his father was just 17 and facing treatment for testicular cancer. Many young men with cancer are in "emotional turmoil" said doctors yesterday and find it hard to think of a future where they might want children, but this 17-year-old came to the decision to freeze his sperm.