If you're translating from an ungendered language and have to choose, the only way you're going to get anything sensible is from context and common usage. Which is going to choose "she is a nurse" because an algorithm that can deduce that fathers are most likely male can also deduce that nurses are most likely female. But without that you get bad translations like "she is a father" and "he is a fine ship" and "John is her own person."