The 38-year-old singer has a son Axl with actor husband Josh Duhamel, whom they welcomed in August last year, reported People magazine.
"(His style is) different on different days because Mommy dresses him. Sometimes he's a complete rocker, sometimes we go hip hop, sometimes we go athletic (and) sometimes he'll wear some North Dakota-inspired clothes," Fergie said.
"I love trying different sneakers on him. That's always fun. I love anything costumed, anything with a theme. I love mixing up his fashion," she added.