Lauren took to Instagram to announce the happy news.
'Then there were five! Welcome to our beautiful Perla Dolly Newton Welsh. We are all thrilled and she really is a doll,' she wrote.
Lauren is also mother to sons Sam, 11, and Monty, two, and daughters Eva, nine, and Lola, six, with her husband Matt Welsh, 42.
Lauren announced her pregnancy on Instagram last year: 'Can't believe this gorgeous four will become five at the end of the year!'
'It will be busy but wonderful. I am lucky to have some great little helpers!' she added.
Lauren also kept her followers up to date with her pregnancy news. 'Counting down the days. I've been told it's a big baby. It's probably all the Milo I've been having!' she wrote.
Previously Bert opened up about his joy of being a grandfather.
'They wouldn't realise it at the moment, but they have made this one of the happiest times of my life,' he said.
'There is that old saying, "The wonderful thing about being a grandfather, or grandparent, is that you give the kids back".
'But in the case of Patti and myself, we don't want to.'