Well, I wouldn't be happy about it and would try to avoid it in the future, but it's done and personally I wouldn't worry about it. I think we all are exposed to odors like that more than we know. Most cleaning supplies have ammonia, so everywhere you go it is in the air.
Ammonia is one of the few things that makes me have an almost asthmatic reaction. I start coughing horribly and can hardly breathe. So I know how gross it is. At the place I used to work, if I had to go in early in the morning it was always in the air as they had just cleaned the floors.
Are you going to have to be around it again? I am assuming you had to be in the room to kind of direct the person who was doing the blueprints? If not, I'd just say, I'm sorry, but I'll need to leave the room and get some air for a minute; I'm pregnant and that odor really bothers me." Or something like that.