The couple welcomed their first child via gestational surrogate on August 29 and he now graces the cover of Life & Style.
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"I had always heard that when you have a baby it completes your life - and it's true," Giuliana said. "I love my baby, and I love my new role."
While Bill claimed that his wife has become "supermom", Giuliana added that she is "happier" than she has ever been.
Giuliana also admitted that she is thrilled to become a mother after the couple's well-publicised difficulty conceiving, saying: "I couldn't believe that all those years of struggling and the tears actually paid off. Every shot, every doctor's visit - in the end, when you're holding your baby in your arms, you forget it all, and it's worth it."
She has previously tweeted that she and her husband "couldn't love little Duke any more than we do", adding: "He's a dream."
