My doctor says I need a d&c becuase I had a miscarriage, but is there another way to get rid of the baby that doesn't require surgery?

Natural or not. Most miscarriages are completed on their own, but if you have retained some part of the conceptus, then you will require a D&C to completely evacuate your uterus.
Pros & cons of D&C. A D&C is simple & routine after a miscarriage. It is an invasive procedure & as such carries some risk. On the other hand, retained tissue has a reasonably high risk of becoming infected by common germs & sets a patient up for a more invasive emergency procedure to try to salvage the womb before real damage is done. A good discussion with your OB should clarify the issue.