Assuming you are talking about Glowlight Danio, they don't get pregnant, they are an egg-scatterer species. She will become gravid (ie full of unfertlilised eggs). At this point, she will scatter the eggs, and the male will fertilise them within a few hours. Generally, they will then eat the eggs.
That's a "piece of string" question, it depends on a number of factors. If you are actively trying to breed them, there are a few things you can do to stimulate spawning. If you aren't, then the chances of you actually getting any fry are fairly slim, although not unheard of.