The former EastEnders actress took to the micro-blogging site to reveal that she and her actor husband Tom Ellis are expecting their second child.
Tamzin, 41, wrote: "Yes,we are very happy to say that we are expecting baby no2 later this year.thanks for all your lovely messages."
She and her 32-year-old husband are already proud parents to four-year-old Florence, and Tamzin has made no secret of her desire to have more children. She said shortly after Florence's birth in 2008 that she did not want to leave it too late as she wanted a bigger family.
The actress is currently starring in Sweet Charity at the Theatre Royal, Haymarket, but has said before that her family comes before her work.
She said: "I am not worried in the least about my career taking a back seat. I want to change my priorities. My career and ambitions have been fulfilled, and I would be quite happy not to work again and look after the children. I don't really have that burning ambition anymore."
As fans Tweeted their congrats to the couple, Tamzin revealed that she had to make an announcement as 'the Spanks (sic) can no longer hide the truth'!
So another celeb baby to look forward to in 2012!