Considering the age and primary gender if nursing student, I think everyone here can say that they knew someone who was pregnant during nursing school
. I was during my BSN (had my ADN, and was going at a snails pace, lol). As a professor, I see it very often.
Not everyone drops out or takes a leave. Some people literally deliver, and come back the next week. Some people try to time it (if it was planned, of course). I think it all depends on the support you have at home. It also depends on yours (and the baby's) health. We all assume everything will go smoothly, but as nurses we know that this is often out of our hands. Physical and emotional (post Partum depression) are bad enough to deal with without the stressor of nursing school.
And don't forget, you WILL need to get some sleep to be productive in school and clinicals.
I think it's advisable to have a realistic plan B, in case you you cannot return right after you deliver. Make sure you know exactly how many days you are able to miss. A doctors note will not be likely to give you any more days off. Your school will treat it like any other illness, and give you the option to withdraw or take an incomplete.