She wrote on her fansite: "Chris, Lexi and I are delighted to announce that I am pregnant and we are expecting a little girl."
On Twitter the actress announced ecstatically: 'Lexi's question of the day(and most days) "Mama when are you going to get a baby in your tummy?"Happy to say TODAY Lexi!Mama is pregnant!Yay'
She followed shortly afterwards: 'OMG! Am overwhelmed with all your tweets! Thank you Thank you Thank you!!! Am thrilled and terrified all rolled into one!'
In February she suffered the stillbirth of her son - seven months into her pregnancy. She had already suffered a previous miscarriage in 2010.
Britain's Got Talent judge Amanda has not yet said when her baby will be due. As she already knows she is expecting a sister for Lexi, we presume she is already around 20 weeks pregnant.
Shortly after her initial statement she followed with: "The first half of this year has been unbelievably difficult for us and so we are beyond delighted to share this news with you. My first priority is of course my family. I will therefore be adjusting one of my professional commitments accordingly.
"Due to its physical content this means I will end my contract with Shrek The Musical eight weeks early. I will endeavour to continue the show until the 3rd October. I do however ask you to bear with me as I will be putting myself and this pregnancy first.
"I have taken medical advice and although I am a strong girl and this is 'once again' a good healthy pregnancy I will absolutely not be taking any risks. Your ongoing support for us this year has been so touching. We are enormously grateful. Thank you so much for your understanding. Amanda xxxxxx"
After her son was stillborn, the 40-year-old actress and TV presenter was adamant she would go on to have more children with husband, music producer Chris Hughes.
Amanda, mum to five-year-old Lexi, said: "I am an optimist. I think, as bad as life sometimes gets, there is so much joy and so much good stuff that there is a balance. Although what happened is obviously horrifying, we can go on to have more children."
Amanda also explained how the experience has brought her even closer to Chris, who she descibes as her 'rock'.
"We argue and bicker like all couples, and Chris calls me The Lip because he thinks I talk too much. But he is the love of my life and I am his and – how lucky – he is also my best friend, which is why we can get through anything. We are polar opposites. He is very private, very closed, and I am pretty much an open book, but together it works. I always think we are like the plus and minus signs on a battery. It wouldn't work without one or the other of us." she says.
She explains that she and Lexi have a catch phrase: "Never give up". "I say, 'Never give up, Lexi', and she says, 'Never give up, Mama'.
Huge congratulations from Parentdish. Wonderful news!