Aren't. Apparate. Floo powder. It isn't mentioned in the books, but St. Mungo's probably does have a maternity ward. Floo powder is probably what they use to get there, but, again, it isn't mentioned.They would also be able to apparate like when dumbldore and harry do right before dumbdore is killed
All the wards were listed. There is no mention of a maternity ward at St. Mungo's.