Judith Rowbotham, a social historian at Nottingham Trent University, said that in the past, birth weights of monarchs were not revealed.
The newest member of the Royal Family, however, will have the details of his arrival pored over by a worldwide audience.
She said the baby prince was a "respectable weight" and added: "It's not champion or a 9lb or 10lb, which would be eyebrow-raising."
"What it certainly shows is that this is a baby of healthy parents. He's definitely got more weight than his father and grandfather did.
"I doubt we were told the birth weights of previous monarchs.
"I'm pretty certain we weren't for George V and George VI. That kind of information would have been seen as very private detail.
"Before, it was enough to know that the child was born alive and healthy. After that, the bulletins would go very quiet."
Prince Harry weighed 6lb 14oz when he was born in 1984.
William's cousin, Lady Louise Mountbatten-Windsor, was born prematurely weighing 4lb 9oz in 2004, while Louise's brother Viscount Severn, arrived in 2007 weighing 6lb 2oz.
The Queen's first great-grandchild Savannah Phillips was just slightly heavier than William and Kate's new baby son and arrived weighing 8lb 8oz in December 2010.
The monarch's second great-grandchild Isla Phillips, born In March last year, weighed 7lb 4oz.
The Prince of Cambridge's birthweight falls within the current healthy range of six to nine pounds - and is close to perfect given the extra time in the womb and the inheritance factor of tall, healthy parents.
The average weight of newborn babies is 7lb 8ozs, with lighter babies being classified small for gestational age (SGA) or of low birthweight.
Babies classified as large for gestational age (LGA) weigh more than expected compared with the time spent in the womb, around nine pounds and over, according to foetal growth charts.
The new arrival's weight will be satisfying for both parents and doctors, and is probably slightly more than expected because he was overdue.
Larger than normal babies are not only difficult to deliver but may herald health problems in later life.
Scientific evidence suggests they may be more prone to obesity, diabetes and heart problems when they grow up.
Similarly, although small babies are easy to deliver there may be developmental problems linked to size as countless studies on premature babies have shown.
The growth of the new Royal will have been closely monitored by scans throughout Kate's pregnancy, because failure to thrive in the womb rings alarm bells, suggesting the placenta is not working properly.
Andrew Shennan, professor of obstetrics at St Thomas' Hospital, London and adviser to Tommy's baby charity, said the newborn's weight was "spot-on normal".
He said: "We take into account the ethnicity of the mother, her height and weight and whether it is the first-born - they tend to be a little smaller than children born subsequently.
"This child is well within the normal range for birthweight that we would hope to see."
As a British summer-born baby, however, the newest royal will be one of the youngest in his class, which could put him at a disadvantage early on. A July birthday will mean that the new Prince of Cambridge will start school not long after he turns four.
- Daily Mail
