According to a 2002 article from the Guardian, "[o]ne of the underlying causes of the French Revolution, the disastrous marriage between Louis XVI and Marie-Antoinette, has been brought down to size [pun intended, for sure] by a meticulous investigation into the royal couple's sexual incompatibility. Put simply, the king was endowed with a ' bracquemart [sic] assez considérable' - a rather large penis - and Marie-Antoinette suffered from a condition known in the court as ' l'étroitesse du chemin', a narrow vagina, that made her frigid."
From the "Circumstitions" website:
"I refuse to believe that it is my daughter's fault," the empress [Marie's mother] wrote to her ambassador at Versailles, maintaining demands for an operation on the king even after several intimate inspections by doctors. They repeatedly said there was no evidence of phimosis, a narrowing of the preputial orifice, a theory that Zweig [a biographer] insisted on after reading nagging letters from the imperial mother-in-law replying to misleading correspondence from her daughter.
It is widely reported that Louis XVI of France could not father children until he was circumcised. Unfortunately for the story, he was already a father well before the alleged operation. Remondino invented this lie in his history of circumcision. It served his need to find historical precedent for circumcision in Europe, to make the ritual seem less alien and more familiar. These were calculated lies without any historical basis. A more scholarly study from France (Le phimosis de Louis XVI (1754-1793) aurait-il été a l'origine de ses difficultés sexuelles et de sa fecundité retardée? [Prog Urol. 2002; 12(1):132-7] by G. Androutsos) thoroughly debunked this myth.