Just an idea: what could be the consequences of Margaret of Valois becoming pregnant of Henry of Navarre and having a son? I know that IOTL they lived separate lives, openly keeping lovers, but let's assume that she gets pregnant in 1572, during the six days between her marriage and the Massacre of St. Bartholomew, and so gives birth to a healthy son in June 1573. How could this affect Henry, Margaret and the religious and political conflicts during the reigns of Charles IX and Henry III?