By: By Rachael Rettner, Senior Writer
Published: 07/16/2013 07:37 AM EDT on LiveScience

The world is eagerly awaiting the birth of the royal baby, but considering this is Kate Middleton's first pregnancy, is the baby likely to be late?

Buckingham Palace has not provided an official due date for the baby but has said the newborn is expected in mid-July.

Babies don't always arrive when they're supposed to, and mothers often say firstborns tend to be late, although this conclusion is typically based on anecdotal reports. [See 11 Big Fat Pregnancy Myths].

Recently, Allen Downey, a professor of computer science at Franklin W. Olin College of Engineering in Needham, Mass., did an analysis to find out if there was any truth to this old wives' tale. Downey studied a 2002 Centers for Disease Control and Prevention survey of 7,643 women, who reported 9,148 live births.

He found that first babies were, indeed, slightly more likely to be born late, at 41 weeks or later, compared with other babies (second-borns, third-borns, etc.)

The results showed that a firstborn baby has a 15 to 16 percent chance of being born late, compared with a 9 or 10 percent chance for other babies. Most babies were born at 39 weeks of pregnancy.

However, the study also found that firstborns were also more likely to be born early, at 37 weeks or earlier.

So, in general, firstborns were less likely to be born on time, said Downey, who is the author of "Think Stats" (O'Reilly Media, 2011). It's possible that first babies may be less likely to be on time because the date of conception is not accurate, Downey said.

Dr. Jill Rabin, chief of ambulatory care, obstetrics and gynecology at Long Island Jewish Medical Center in New Hyde Park, N.Y., noted that a baby's due date is an estimate, and it's normal for babies to arrive two weeks before or after that day. Therefore, although parents may perceive a baby to be "late" if it arrives two weeks after the due date, this is not really the case.

"When you're expecting a first baby...you're locked on to the due date, and you expect the baby on that due date," Rabin said. But even if a woman thinks she knows exactly when she conceived, "it still can be two weeks high or low, and it's considered normal," she added.

Rabin said there is no known biological reason why firstborn babies would be more likely to be early or late.

After 42 weeks of pregnancy, a baby is considered overdue, Rabin said, and doctors become concerned about complications, such as an aging placenta that is not able to deliver proper nutrition to the baby.

According to the Mayo Clinic, a woman may be more likely to have an overdue baby if the baby is male. Will the royal heir be a boy?

Follow Rachael Rettner @RachaelRettner. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.com.

Copyright 2013 LiveScience, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. ]]>

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  • A note is left by a member of the media on stepladders placed to get elevated positions across from St. Mary's Hospital Lindo Wing in London, Monday, July 8, 2013. Major media outlets are seeking positions outside the building where Prince William and his wife Kate are expecting their first child to be born in mid-July. (AP Photo/Lefteris Pitarakis)

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the Media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Royal baby

    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the media reserve a place outside where the Duchess of Cambridge will give birth later this month.

  • Preparations Begin Ahead Of The Birth Of The Royal Baby

    LONDON, ENGLAND - JULY 09: Public Relations Executive of Ladbrokes, Jessica Bridge, writes today's odds for the royal baby on a chalk board in front of the Lindo Wing as the UK prepares for the birth of the first child of The Duke and Duchess of Cambridge at St Mary's Hospital on July 9, 2013 in London, England. (Photo by Jordan Mansfield/Getty Images)

  • Preparations Begin Ahead Of The Birth Of The Royal Baby

    LONDON, ENGLAND - JULY 09: A Ladbrokes chalk board shows today's odds for the royal baby on a chalk board in front of the Lindo Wing as the UK prepares for the birth of the first child of The Duke and Duchess of Cambridge at St Mary's Hospital on July 9, 2013 in London, England. (Photo by Jordan Mansfield/Getty Images)

  • Preparations Begin Ahead Of The Birth Of The Royal Baby

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  • Preparations Begin Ahead Of The Birth Of The Royal Baby

    LONDON, ENGLAND - JULY 09: Public Relations Executive of Ladbrokes, Jessica Bridge, poses for a picture with today's odds for the royal baby on a chalk board in front of the Lindo Wing as the UK prepares for the birth of the first child of The Duke and Duchess of Cambridge at St Mary's Hospital on July 9, 2013 in London, England. (Photo by Jordan Mansfield/Getty Images)

  • Royal souvenirs and postcards are displayed outside a shop in London, Monday, July 8, 2013. Britain's Prince William and his wife Kate are expecting their first child to be born in mid-July. (AP Photo/Frank Augstein)

  • Royal souvenirs are displayed in a shop window in London, Monday, July 8, 2013. Britain's Prince William and his wife Kate are expecting their first child to be born in mid-July. (AP Photo/Frank Augstein)

  • Members of the media wait outside St. Mary's Hospital exclusive Lindo Wing in London, Monday, July 8, 2013. Major media outlets are seeking positions outside the building where Prince William and his wife Kate are expecting their first child to be born in mid-July. (AP Photo/Lefteris Pitarakis)

  • Members of the media wait across from St. Mary's Hospital exclusive Lindo Wing in London, Monday, July 8, 2013. Major media outlets are seeking positions outside the building where Prince William and his wife Kate are expecting their first child to be born in mid-July. (AP Photo/Lefteris Pitarakis)

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  • Journalists put sweepstakes on a wall to bet for the time the royal baby will arrive at the entrance to the Lindo Wing at St Mary's Hospital in London, Friday, July 5, 2013. Media are preparing for royal-mania as Britain's Duchess of Cambridge plans to give birth to the new third-in-line to the throne in mid-July, at the Lindo Wing. Cameras from all over the world are set to be jostling outside for an exclusive first glimpse of Britain's Prince William and the Duchess of Cambridge's first child. (AP Photo/Frank Augstein)

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  • BRITAIN-ROYALS-BABY-MEDIA

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  • Members of the media pass time across the street from St. Mary's Hospital exclusive Lindo Wing in London, Friday, July 5, 2013. Media are preparing for royal-mania as Britain's Duchess of Cambridge is due to give birth to her baby in mid-July, at the Lindo Wing. Cameras from all over the world are set to be jostling outside for an exclusive first glimpse of Britain's Prince William and the Duchess of Cambridge's first child. (AP Photo/Lefteris Pitarakis)

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  • Members of the media pass time across the street from St. Mary's Hospital exclusive Lindo Wing in London, Friday, July 5, 2013. Media are preparing for royal-mania as Britain's Duchess of Cambridge plans to give birth to the new third-in-line to the throne in mid-July, at the Lindo Wing. Cameras from all over the world are set to be jostling outside for an exclusive first glimpse of Britain's Prince William and the Duchess of Cambridge's first child. (AP Photo/Lefteris Pitarakis)

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    Members of the media mark up their selections for a sweepstake bet on the time, date and sex of Prince William and his wife Catherine's baby outside of the Lindo wing of St Mary's Hospital in London on July 5, 2013. Prince William and his wife Catherine's baby, which will be third in line to the throne, will be born in the private Lindo wing of St Mary's Hospital, where William was born in 1982 and his brother Harry in 1984. AFP PHOTO / ANDREW COWIE (Photo credit should read ANDREW COWIE/AFP/Getty Images)

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    A collection of ladders stand outside the Lindo Wing of St Mary's Hospital in Paddington, London as members of the Media reserve a place outside where the Duchess of Cambridge will give birth later this month.

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