[2] Claude was victim of the unhealthy traits that Catherine appeared to pass on to all her children with the exception of Marguerite, and suffered from a hunchback and a club foot, and during her childhood she was frequently vulnerable to various diseases.

[citation needed] On 19 January 1559, at the age of 11, she married Charles III, Duke of Lorraine in the cathedral of Notre Dame in Paris.

[3] The marriage was arranged as a symbolic union of peace between France and Lorraine, after Charles III had spent his childhood as a hostage at the French royal court, and completed after the Treaty of Chateau-Cambresis.

For some time, their mother and brother, the Duke of Anjou, had come to believe that there was a romance between Margôt and Henry of Guise, nicknamed le Balagré ("Scarface") whose family the Valois distrusted and disliked.

Claude arranged the marriage of the Duke of Guise to the Princess of Porcien, and mediated for her family members, explaining to her mother that the supposed romance between Margôt and Navarre was nothing more than a vicious lie invented to discredit her.