Differnet things. I think the most common cause is an abnormality in the sperm or egg. This is nature's way of ensuring that you end up with a healthy baby. An abnormal sperm or egg would not usually end up in a healthy baby and so it is naturally aborted (if you want to use that term). There are other reasons, as well but I hear that is the most common and miscarriages are very common btw. They say over 80% of women will have at least 1.
at 12:44 PM on Oct. 20, 2009