"It's a boy!" announced Britney Spears, then 23, on her website following the birth of her son Sean Preston (with then-husband Kevin Federline. The starlet (pictured after an appearance on the Late Show with David Letterman with 7-month-old Sean) had always been open about her desire to be a mom. "A lot of people think you should wait till you're older to have kids. I've had a career since I was 16, have traveled around the world and back," she has said. "The only thing I haven't done is experience the closest thing to God, and that's having a baby. I can't wait!"