I believe my wife (a recovering alcohollic) could be drinking mouthwash while pregnant.

If she is drinking enough to get a buzz (and that is possible, there is alcohol in mouthwash), then I would worry about fetal alcohol syndrome and get her away from that stuff quickly.

Tick

It really would depend on the amount she may be ingesting, but in some ways, again depending on how much she may be drinking, it can be worse than regular alcohol.

Obviously it would be wise to get rid of any mouthwash with alcohol in it and purchase one of the non-alcoholic versions.
It would also be wise to speak to your wife about your concerns so that she can get the help she may need if she is indeed looking for ways to get some alcohol.