Medical historian Whitney Wood first became interested in the history of women's pain through an undergraduate course that described the practice of "twilight sleep."

Wood, who is the new Canada Research Chair at Nanaimo, B.C.'s Vancouver Island University, says twilight sleep was a form of anesthesia that was popular in the early 20th century, administered to women in labour.

The drug mixture contained a blend of anesthetic and amnesia drugs. Labouring patients would still experience pain in giving birth, but the amnesiac part meant they didn't remember it.

At the same time, the drugs made women extremely excitable and sensitive to stimulation, prompting them to jump out of bed and injure themselves, Wood said.

This meant that the labouring mother would often have to wear a straitjacket and a blindfold to restrict stimulation and control her movements. 

"From our modern perspective this sounds horrific ... but for many women in the early 20th century this was a good type of birth and women actively sought this out," Wood said. "My main question was why."