The former Girls Aloud star, who is already mum to son Bobby, 21 months, broke the happy news in an exclusive interview with HELLO! magazine, saying that she and husband Justin Scott had been hoping to conceive again since their romantic Barbados wedding in February 2016.
'We knew soon after we got married that we'd be very happy for baby number two to come along. When I first met Justin 14 years ago, I told him I wanted four children. We're both over the moon,' she told the mag.
'Before I had even taken a test, I knew it instinctively. I wasn't suffering from morning sickness but telltale changes in my body made me certain I was expecting.'
'When I took a home test early one morning to make sure, it confirmed what I'd already sensed. I was thrilled. The first thing I did was to wake up Justin and tell him, "You're going to be a daddy again!"'
https://www.instagram.com/p/BG1A5qBBHac/?taken-by=kimberleywalshofficial&hl=enKimberley's son Bobby and husband Justin, pictured together on Father's Day 2016
Kimberley added that she couldn't keep the news from former bandmate and best friend Cheryl, 'When Cheryl came over to visit, I couldn't keep my pregnancy a secret any longer.
'She was so happy for us and thinks it's great to keep our family growing and that there will be a small age gap between Bobby and the new baby.'
She also revealed that she and Justin had not chosen to find out the sex of their new arrival after their 12-week scan.
In an interview with HELLO! shortly after her wedding, Kimberley said that Bobby was ready to be a big brother.
'Bobby has started rocking his arms like a cradle and saying, 'Baaaaybee',' she said at the time. 'I definitely want more children... Bobby is so sociable, he loves other kids so he'd definitely enjoy it.'
'For him to grow up with a sibling close in age to him would be lovely, so yes fingers crossed!'