Haha:
"Modern medicine has reached the unprecedented level. People eat better food than thousand years ago. Huge armies of doctors and modern medications serve for people’s health, which makes it possible to live a long happy life with one kidney. Moreover, the second kidney is redundant, because it wastes resources of the body. It's more than likely that in the nearest future it will be ablated just after the child has been born as it already often happens with appendicitis (note: you can do preventive surgical removal of appendicitis in our clinic too)."