Hollywood's Hottest Moms

After welcoming second son Zuma, Gwen Stefani wasted no time before heading back to the gym. Trainer Mike Heatlie put Stefani through high-intensity resistance sessions— a series of simple exercises made more challenging by cutting out rest periods in between sets— four times a week to work off her pregnancy pounds. "I've tried yoga and Pilates before, but I just prefer old-school fitness workouts," Stefani says.