A girl I worked with said that her doctor told her that it would be okay to have a little bit of wine when she was pregnant, but not to overdo herself. I really don't know what overdo is either, but he said it was alright to have a tiny bit.
Just from a cook's standpoint: wine is used to add a little bit of flavor to something. Wine has a very strong taste to it and I doubt he put very much in the soup or you would have been able to taste it, probably a 1/2 cup to a cup if that. It probably was just to add a little zing and bitterness. I wouldn't get too worried about it. I looked up a onion soup recipe and the most I see in the ingredients is a cup.
If you are pregnant though you will want to make sure you don't take in alot of alcohol (beer, hard liquor, etc) as it can be harmful to a baby if enough is ingested.
If you are really worried about it, ask the doctor. You could probably even call the pharmacy and they could help you.
Hope I was able to help some...