The 34-year-old singer said she is extremely excited and looking forward to her pregnancy, reported Femalefirst.
"We want the surprise. I don't have a preference. I think it would be lovely for Bobby to have a little brother so close in age but I'd also love to have a daughter, so I can't really lose."
Walsh said she and her husband are also ensuring that her two-year-old son does not feel left out after their second child.
"He's a little bit too young to fully understand but he knows there's a baby in my tummy. He pretends it is kicking him!