Something else to keep in mind, if it is your dream to be a obstetrics nurse, is that these units often do not hire new nursing graduates. You might have to spend a few years working in another part of the hospital - usually med-surg (medical-surgical, the sort of "regular" floor). I do know someone who was fortunate in being able to start in the NICU - she had done an externship there and had a lot of connections. (Now she likes it so much she doesn't want to leave.)
I guess my point is mostly that nursing is a wide career and you don't necessarily know where it will take you. It's fine to think that you would like to work in this environment, but keep in mind that it may be a ways off.
While you wait, or instead, you could get involved with childbirth as a doula and get a lot of practical childbirth experience!