When can I take my new baby out in public? I’m afraid she’ll catch a cold—but I need to run errands. What should I do?

I don't see why not? It's pretty common nowadays to see newborns outside homes for vacinnations, jaundice check ups, etc. Just have to ensure that baby is sufficiently dressed. The rule of thumb is that baby should be dressed "one more layer" than you are, esp if they are in strollers. Also, don't forget to occasionally check on baby's temperature and see if baby is hot or cold, bearing in mind that this is SG (hot outside, cold inside)