Stretch Marks
Stretch marks can be deep purple in colour and will generally fade to white after you've given birth but will never fully disappear. They arn't herreditory and can't be prevented by rubbing creams into you stomach (although this will help with itchiness and make you feel better).
Varicose Veins
These can be prevented or lessened by wearing support stockings, gentle walks (increases circulation), drinking plenty of fluid, sitting with your feet up, not standing for to long at a time.