Cameron Diaz is close to signing on for the lead role in Lionsgate's adaptation of What to Expect When You're Expecting.

The project is based off the best-selling book of the same name written by Heidi Murkoff, which has sold more than 16 million copies. The story of the movie will revolve around five couples who are all expecting their first child.

Shauna Cross (Whip It!) and Heather Hach (Freaky Friday) adapted the book. We reported in March that Kirk Jones (Everybody's Fine) will direct What to Expect When You're Expecting.

Production is scheduled to begin in July on What to Expect When You're Expecting, after Cameron Diaz wraps production on Gambit, which started shooting today.