Plus SO often implies OP was a citizen and then SO comes in on a priority VISA program. They do check to ensure you really are romantically involved. There are a number of poor who decide nearly any American is a better life than they could have at home and so will sign up for a blind marriage to anyone. A doctor likely has means to do some verification of a potential mate before committing, but if they find life bad enough back home they can have low standards. (from what I can tell it mostly works out for those doing this - some get abused, but most seem to have a good life)