I think it has more to do with how much stress you have from your job, and
if there is any negative factors (to the unborn baby) in your working
environment. If there is risk that you don't want to take, then it's better
to quit. (I did.) Physically, everyone's experience is different... you
can give yourself some time to find out if you're having a smooth pregnancy
or one that makes you very tired or uncomfortable.
Generally speaking, 2nd trimester is more comfortable than 1st because most
people stop having morning sickness by then. You will feel more energetic
and even enjoy being pregnant. I stayed home for my third trimester because
I didn't want to deal with long hours and stress from work. But I didn't
get much done staying home... just relaxed and enjoyed the freedom. (For me
it became hard to move around in months 8 &9.) You'll have to ask yourself
if you are okay with not being productive (lack of sense of accomplishment
because not working), as some people would be bothered by it. No matter
what you decide, don't regret it after. Try to enjoy this time when baby
goes where ever you go, it's a lot harder once your baby is older than 3
months (becomes more and more active). Good luck!