Wow. Talk about a roasting! I was asking a question, surely that's what AIBU is for? Or is it for the more sanctimonious among us to come and rain judgement down on someone for asking a question? 
For the record;
a) I work for a company (and in a country) where if you are sick, you are sick. You email in the morning and say 'I am sick, I need x days off' and it is accepted. If you're off for more than 4 days in a row, you need a Drs note, but it is easy to get an appointment, they are more than happy to provide them (in fact they offer to do so in most cases) and no further questions are asked. There is no limit to the number of sick days you can take in a year (unless it's long term sick in which case pay is eventually affected) and there are no 'sanctions or punishments'. This does not make for an environment in which people take the piss and the 'economy grinds to a halt' - I work in Germany, the strongest economy in Europe - but it does make for an environment in which people normally understand that going into the office while sick just a) prolongs the illness and b) spreads it, and feel comfortable and safe not doing so.
b) I wasn't ever going to 'tell her to take time off', I was going to suggest that she can WORK from home if she wants to. She's new and quite young and maybe doesn't understand that this is an option. She might be feeling really bloody miserable sat at her desk with a cold. I would be.
c) How TF is it 'precious' not to want to get sick? I have a really, really full plate at the moment, between a really difficult situation at home, a ridiculously full-on job, constant travel and trying to cope with a totally unplanned pregnancy which is leading to a LOT of sleepness nights. Surely it's ok for me not to want to get sick as well. I'm not talking 'the sniffles' here, this girl is really quite ill. It's not that I think it will affect my pregnancy or damage my 'PFB' in any way, I know it won't. But I also know it'll make me damn miserable for a few days, and surely no-one wants that if it's avoidable?
d) To answer the question about immunity and pregnancy...apparently so, yes! I discovered this recently. Apparently your immune system has to function at a lower level because otherwise it'd recognise the baby as a 'foreign body' and attack it. Who knew?!
I shall know better than to ask AIBU in the future...