Which begs the question, since Superman is inherently infinitely stronger and more powerful than mere humans, which he hides in his everyday life, would not sex with him [or his son] qualify as incredibly dangerous?
Larry Niven speculated about this (at least the hetero version) many years ago, in a piece called “Man of Steel, Woman of Kleenex”. Worth a read.
Super STDs. Resistant to every antibiotic.