With Kate Middleton overdue a week from her initial due date of July 13, reporters have queued up outside the Lindo wing of St. Mary's Hospital for a first peek of Kate and Walliam's baby.

According to a recount of William's birth, Princess Diana "had to be induced" when she gave birth to the Duke of Cambridge on June 21, 1982.

Diana said to journalist Andrew Morton, "I couldn't handle the press pressure any longer, it was becoming unbearable," reported People. The Princess added, "We went in very early. I was sick as a parrot the whole way through the labour, very bad labour."

Kate too was hospitalised for morning acute sickness during the initial stages of her pregnancy.

The National Institutes of Health offered its own explanation of why Kate's baby is late: Though the average pregnancy has a duration of 40 weeks, it is not considered late until the pregnancy is in its 42 week. The NIH also said that first pregnancies are almost always late. Research suggests that first babies are normally eight days late.

According to the NIH guideline, the royal birth may take place on Saturday or after.

There is also some evidence that suggest that late babies are usually male. Factors that contribute to late pregnancies also include a genetic disposition toward late pregnancy, obesity and rare problems with the foetus.

The Centre for Disease Control says that Kate' s due date is just an approximation and not an exact science. The number of post-term pregnancies has declined about 50 per cent to figures in 1990 in the U.S. with about 5 per cent of pregnancies going beyond the 42-week mark.

An online report by E! News also said that doctors in the U.K. do not induce labour unless the delivery date is a week to ten days off base. Kensington Palace is carrying out its day-to-day activities as if Kate is a few days late, say reports.

William and Kate have left her parent's home in Bucklebury and thought to be headed back to London. They are expected to check into St. Mary's Hospital when it is closer to actual arrival date.

However, the couple have selected an alternative arrangement just in case they can't wait till get to St. Mary's on time. They will go to the Royal Berkshire Hospital, where Kate was born in 1982.