Katie, who is believed to be around six months pregnant with her fourth child by new husband Keiran Hayler, said: "I would say to anyone out there who is pregnant, do your own thing."
Katie, 35, has three children, Harvey, 11, Junior, eight and Princess, four.
She said the Duchess of Cambridge should do whatever she feels is best - despite the well-meaning advice she will get on breastfeeding over bottle-feeding and instructions to 'do this, do that'.
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"Do whatever you want to do," she said.
Katie made her comments as she promoted her new perfume 'Kissable' - hiding her own baby-bump with a pair of giant lips, as you do...