I have a good friend who is a male midwife. Why is that so much different than being a male OB/Gyn? And, what's the difference between those two than a male nurse working in maternity? You're there as a health care professional, if you practice nursing with confidence (in whatever area of nursing) your patients will usually respond appropriately.
If you're in a large, metro area where you have international patients or different cultures or religions that do not share our philosophies about allowing opposite genders to treat patients, you may encounter some (possibly serious) issues. I've been a nurse for years, and have heard only one problem of this kind. A man refused to allow any other male inside his wife's delivery room--no male doctor, no male nurse, no male from food services dropping off her lunch tray. Surprisingly, the hospital caved in because it was a religious belief and pulled the male nurse who was assigned to that patient. We debated the issue for months (years!) afterward, with some nurses saying, "what next? a racist patient who refuses to have a minority nurse?" and others saying, "but, it would only hurt the female patient, because he could abandon her if another man saw/touched her body" Both positions are legitimate. It's a real ethical dilemma... but one you probably won't be dragged into!