It is fair to say that anyone who displays a depressive disorder prior to delivery of a child is more at risk of post partum depression than is a person with no history of depression. But post partum depression is treatable, and there's no reason to let worry about it interfere with your plans for a family. Remember that Andrea Yates' treatment had been interrupted - if her treatment had continued it is probable that the tragedy would never have occurred. Depression is a treatable condition, and most people who display it lead normal, productive lives. Treatment is the key.