Criteria for different types of nursing

I'm not sure what you mean by criteria. All that is required is a RN license (sometimes a BSN degree too, depending on the position and hospital). Many places will orient a new grad to their preferred area, while others require 1-2 years experience in med-surg. Depends on how badly the nursing shortage has affected that area.

Here's a link to some info about the nursing specialties you were interested in. They list info on trauma and perinatal specialties.

1st. CARE
2nd. Know what you're doing.