Celebrity The Ladies of What to Expect When You're Expecting and More! By InStyle Editors InStyle Editors Instagram Twitter InStyle's mantra is "Everybody's in," and that means anyone who finds their way to our stories should find themselves reflected in them. We prioritize bringing the right writer to every story and sometimes collaborate as a team to ensure we're including points of view across race, gender expression, body size, skin and hair type, and more. Our editors and writers comprise decades of expertise across the beauty, fashion, lifestyle and wellness spaces in print and digital. We prioritize journalistic integrity, factual accuracy, and also having fun with every story we share. For more about our team, click here. InStyle's editorial guidelines Published on May 15, 2012 @ 01:30PM Pin Share Tweet Email Photo: Kevin Winter/Getty Images What did we expect at the What to Expect When You’re Expecting premiere? Nothing less than pretty off-the-runway looks from the cast’s leading ladies: Brooklyn Decker (in Giambattista Valli), Elizabeth Banks (in Alexander McQueen), Cameron Diaz (in Valentino), Jennifer Lopez (in Maria Lucia Hohan), and Anna Kendrick (in Elie Saab). As for working on a film about the pleasures—and pains—of pregnancy and becoming a mom, Banks said: “It was a great, really familiar thing.” (Banks is mom to son Felix.) So what’s her one mommy must-have? “Great help,” she said. “Grandma, for instance!” See more stars at last night’s hottest parties in the gallery. — Caitlin Petreycik, with reporting by Andrea Simpson