Original: Catherine gave birth to her only child -- a daughter , Mary Seymour , named after her stepdaughter who would go on to become Queen Mary I of England -- on 30 August 1548 , and died only six days later , on 5 September 1548 , at Sudeley Castle in Gloucestershire , from what is thought to be puerperal fever or puerperal sepsis , also called childbed fever .
Simplified: She gave birth to their daughter , Mary , at Sudeley Castle on 30 August , 1548 , but she did not recover from the birth and died soon afterwards on 5 September , 1548 .