As many as 15 percent of new moms become depressed or experience anxiety after giving birth — and if left untreated, postpartum depression (or PPD) can result in long-term problems for both the baby and the mother. Still, many sad moms stay mum about their blues. Why? One of the biggest stumbling blocks to getting depression treatment is that many new mothers feel guilty about their feelings and don't ask for help. To help clear the stigma, a few celebrity mamas have opened up about their own experiences with postpartum depression. From Gwyneth Paltrow to Princess Di, here’s a look at some famous women who fought PPD.