Nicole poses with the six-week-old on the cover, and is joined by husband Joel and 21-month-old daughter Harlow for an inside spread with interview.
"I couldn't be happier," Nicole tells the mag. "The only thing you want is for your kids to be healthy and happy, and they are. I'm right where I belong."
"I'm glad I had a girl before I had a boy," she adds.
"[Harlow] just loves him so much," explains Joel. "She's very gentle with him."