Katie Price is reportedly terrified of going into premature labour following revelations her husband has been having an affair.

The 35-year-old star - who recently announced that she was six months pregnant with her fifth child - revealed on Twitter last week that her husband of just over a year, Kieran Hayler, had been having a ''full blown sexual affair'' with her former best friend Jane Pountney, and she's now said to be worried that the stress is going to cause her to go into early labour.

A friend of Katie's told the new issue of Now magazine: ''Her stress levels and blood pressure are sky high. She was terrified she was going to lose this baby before all this stress. You can't imagine how worried she is about the effect this is all having on her unborn child.''

The former glamour model, who gave birth to her and Kieran's first child Jett - now nine months old - two months early during an operation that took her and her son weeks to recover from, was advised to look after herself and her new baby by trying to avoid stress.

Another pal revealed: ''Her doctor warned her before all of this that she had to take care of herself and keep her stress levels down. Goodness knows what this is doing to her blood pressure. We're all so worried about her.''

Speaking about her shock pregnancy last week, Katie confessed that she had already experienced a scare, but that Kieran had helped her through it.

She said: ''I felt these awful pains. That was terrifying because you know you don't know what's going to happen.

''[The doctor] knew immediately what was wrong - there were complications. All I thought was, 'Thank God Kieran's with me.' He was brilliant. The doctor explained what steps I would need to take to keep the baby and myself healthy. I was scared I might lose the baby.''