Have you told your dr. your concerns. They used to believe that it increased your risk of miscarriage, but it has been found in the past couple of years that it is less likely than they used to think. I imagine the reason the doctor wants to do this now is to make sure that there are no abnormalities in the baby because of your risk of miscarriage. That way you might still have time to terminate the pregnancy if you found out there was something wrong with the baby.
The decisions comes down if you would be willing to carry the baby to full term even if there was something that was wrong which is probably unlikely, but something to consider.
I would tell your doctor your concerns about the cvs causing a miscarriage and they can help you look at all of the pros and cons.
Here is an article that might be interesting for you and help put your mind at ease:
http://www.acog.org/from_home/publications/press_releases/nr08-31-06-1 .cfm



