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 Princess Elizabeth holding Princess Margaret as a baby, watched on by the Queen Mother.

Credit: Getty Images

Princess Margaret was known as the wild child of the Royal Family in her day, especially when compared to her more serious older sister, Queen Elizabeth. But according to a shocking new royal biography, Princess Margaret suffered from fetal alcohol syndrome due to the Queen Mother’s excessive drinking while pregnant—a habit she seemed to have avoided when carrying the late Queen.

Pulitzer Prize-nominated biographer Meryle Secrest has written Princess Margaret and the Curse, examining Margaret’s life based on the speculation that she had an “invisible disability” due to fetal alcohol syndrome (via the Telegraph). Babies who are exposed to alcohol during pregnancy can have a “wide range of physical, behavioral, and cognitive impairments,” per the National Institute on Alcohol Abuse and Alcoholism.

“The book says that while Margaret lacked the syndrome’s tell-tale smooth lip philtrum and small eyes, she did display characteristic mood swings, stunted growth, difficulties learning how to write, and painful migraines,” per the Telegraph.

Princess Elizabeth, Princess Margaret and the Queen Mother sitting next to each other on a gold chair wearing floral dresses

The Queen Mother is seen with her daughters Margaret Rose (bottom) and Elizabeth in 1944. | Credit: Getty Images

The Queen Mother, Princess Margaret and Queen Elizabeth wearing head scarfs and coats standing in a row

The trio is seen at the Badminton Horse Trials in 1973. | Credit: Getty Images

Cover of the Princess Margaret and the Curse  book

Princess Margaret and the Curse

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The Queen Mother, who was a heavy drinker, likely wouldn’t have been told to avoid alcohol during her pregnancies as it wasn’t until the 1970s that the term fetal alcohol syndrome even existed, and it was commonplace for women in the 1920s and ’30s—when Elizabeth and Margaret were born—to drink and smoke during pregnancy.

However, it seems that the Queen Mother might not have drank as much as she usually did—or at all—when pregnant with her first child, Elizabeth. Per the Telegraph, the book claims that in a 1925 letter, the Queen Mother wrote to her husband: “The sight of wine simply turns me up! Isn’t it extraordinary! It will be a tragedy if I never recover my drinking powers.”

Citing the research of Dr. Kenneth Jones, one of the two doctors who identified term fetal alcohol syndrome in 1973, Secrest writes that Margaret “had a poor awareness of physical danger” and struggled with impulse control, as many with the condition can do, and would “blurt out the truth.”

However, there’s no definitive proof that Princess Margaret suffered from the disorder.

Princess Margaret and the Curse: An Inquiry into a Royal Life will be released on Sept. 9.