The wife of the CEO of Twitter is showing her devotion to her husband's company by sending 'tweets' while giving birth. Designer Sara Williams updated friends - and hundreds of thousands of strangers - live online after going into labour.

"Dear Twitter, My water broke," she wrote at at 9pm California time (5am GMT). "It wasn't like Charlotte in Sex and the City. Now, timing contractions on an iPhone app."

Her updates quickly spread beyond her own 12,000 followers to become one of the most-discussed topics on Twitter, as users waited for the story to unfold.

Six hours into labour, Mrs Williams wrote: "Epidural, yes please."

Twitter has become a global phenomenon since its launch in 2007, with millions of people posting 140-character updates by text or online.

Mrs Williams is part of a growing trend - spearheaded by her husband's site - of sharing the minutiae of personal life on the web.

Two years ago, Twitter user Paul Saarinen made his daughter Elle an instant web celebrity when he became the first father to tweet updates, pictures and video throughout a birth.

Several more expectant parents have adopted the trend since, despite critics suggesting it violates the privacy of the children.