The pregnant wife of Liberal Democrat leader Charles Kennedy has been admitted to hospital, forcing the party to postpone its manifesto launch.
Sarah Kennedy supported the Lib Dem campaign on Sunday
Sarah Kennedy is expected to give birth during the general election campaign.
Mr Kennedy cancelled his campaigning events for the rest of Monday and returned to London to be with his wife.
His deputy Sir Menzies Campbell will stand in for him. The manifesto, which was due to be launched on Tuesday, will now be unveiled later this week.
Mr Kennedy was due to visit a college in Totnes, Devon, where he was set to highlight some of the Liberal Democrats' education pledges - including 21,000 extra primary school teachers.
But as he waited for the flight at Farnborough Airport in Hampshire, he took a telephone call telling him his wife had been taken to hospital - she is due to give birth in the middle of this month.
He spoke to her briefly on the phone and was driven back to London about an hour later, where she is being treated at an un-named hospital.
Mrs Kennedy appeared alongside her husband on the campaign trail for the first time on Sunday.
A Lib Dem spokesman said: "Sarah Kennedy has been taken to hospital. She is fine.
"Charles Kennedy has returned to London to be with her. In consequence, the Liberal Democrat manifesto launch tomorrow has been postponed."
The party will still hold a news conference about the economy on Tuesday and Sir Menzies will take Mr Kennedy's place on a visit to Bristol.
Sir Menzies told BBC News he would be fulfilling Mr Kennedy's engagements "for the next day or two".
"This is a contingency we had allowed for in our planning for the general election and I think we have simply taken that particular file out of the drawer," he said.
Sir Menzies said the party's campaign had always been a team effort, adding: "It does not mean Charles is out of the election altogether.
"He will obviously continue to take a part, give advice and participate in those parts of the election campaign and its planning that do not require him to leave the bedside of his wife."
Lib Dem frontbencher Paul Tyler filled in for Mr Kennedy at the Totnes event.
The Kennedys attended the royal wedding celebrations on Sunday
Speaking to Radio 1's Newsbeat shortly before hearing his wife had been admitted to hospital, Mr Kennedy said he was "very nervous, apprehensive, excited" about the birth.
When asked if he was looking forward to changing nappies, he said: "I dare say that will do me good, I've been getting some theoretical demonstrations of this with Sarah, my wife, already...
"There's an altogether new man you've got sitting here."
Earlier, he told GMTV: "Sarah is keeping fine and she is a fantastic support and a valuable asset for me.
"The priority for an interlude will be Sarah and the baby but I will not be forgetting my day job."
Tory leader Michael Howard sent the couple his best wishes, saying: "I hope everything goes very well for Sarah Kennedy and I look forward to sending them our warmest congratulations."
On Sunday, Mrs Kennedy said she was "very well" and really looking forward to the birth.
Mr Kennedy has said he plans to take at least two days' paternity leave when the baby is born.