Randi Anderson knew she was on her own the day her son was born 22 months ago when she drove herself to the hospital. Long before Anderson pulled up to Swedish Medical Center, her film-school boyfriend was gone. Twenty hours after she arrived at the hospital, she joined the growing ranks of single mothers. It is a group that often feels isolated, suffers higher-than-normal rates of depression and believes it carries a stigma in a culture that celebrates marriage. "I certainly feel like it's written across my face," Anderson, 34, said. "We've been told it's not OK to be a...