Hayden Panettiere is pulling back the curtain on some of the darkest chapters of her life ... including nearly dying during childbirth and battling postpartum depression after welcoming daughter Kaya with former fiancé Wladimir Klitschko . The actress sat down Monday with CBS News' Gayle King to promote her new memoir, "This Is Me: A Reckoning" ... and spoke candidly about how what should've been one of the happiest times in her life spiraled into something far more painful. Check out the clip .