Very inconsiderate IMO. Colds & sniffles, that's one thing (in ds's first couple of winters we'd never have met up with anyone if we'd stayed home due to these, lol) BUT the other things edam mentions, well, that's simply not on. Or the dreaded conjunctivitis. Have you discussed it with the other mums? If you have everyone's email addresses, could you send round an email, not directed at anyone in particular, just saying that as the season of general yuckiness is upon us, could everyone be careful about bringing their children along if they have something contagious?