I know undercooked or raw meat is risky during pregnancy because it carries bacteria. is a steak safe to eat medium because all the bacteria can be found on the outside of the meat, which is fully cooked?

Contaminated meat: Undercooked or raw meat is no more risky or dangerous during pregnancy than at any other time. In general, whole meat that is cooked enough to sear the surface protects against bacterial infections, so even very rare or virtually uncooked meat is safe. Ground meat (e.g. hamburger) is a different story, because surface bacteria can be present throughout. Cook burgers at least to medium pink.