Prince William and Catherine Duchess of Cambridge leave the hospital with their newborn baby boy at the Lindo Wing, St Mary's Hospital, London, April 23, 2018. <br><br> Kate Middleton departed St. Mary’s Hospital for Kensington Palace just hours after giving birth, posing upon her departure with William and their son. <br><br> Prince William and Duchess Kate have announced the name of their third child: Louis Arthur Charles. The newborn, the third child of William and Kate, weighed 8 pounds, 7 ounces at birth. He was born at 11:01 a.m., local time. Hannah Mckay/Reuters

Catherine, The Duchess of Cambridge convenes an early intervention for children and families symposium at Royal Society of Medicine, March 21, 2018, in London. Karwai Tang/WireImage via Getty Images

Britain's Catherine, Duchess of Cambridge attends the presentation of Shamrock to the 1st Battalion Irish Guards, at a St Patrick's Day parade at Cavalry Barracks in Hounslow, London, March 17, 2018. Andrew Parsons/Reuters

Duchess of Cambridge Kate Middleton in Stockholm, Sweden, Jan. 31, 2018. Andrew Parsons/i-Images/Polaris

Duchess Kate goes for a test drive Catherine, Duchess of Cambridge, arrives at the Jaguar Land Rover's Solihull manufacturing plant, the first stop of the start of their visit to Birmingham, England, Nov. 22, 2017. Robin Nunn/Nunn Syndication/Polaris

Britain's Catherine, Duchess of Cambridge, drives a Land Rover Discovery as she takes part in an off-road driving experience during her visit to Jaguar Land Rover's Solihull manufacturing plant in Birmingham, England, Nov. 22, 2017. Paul Ellis/AFP/Getty Images

Duchess Kate dances with Paddington Bear Catherine, Duchess of Cambridge dances with Paddington Bear at Paddington Station while meeting the cast and crew from the forthcoming film Paddington 2, in London, Oct. 16, 2017. Pregnant with her third child, Kate announced the baby's due date will be in April 2018. Jonathan Brady/WPA Pool via Getty Images

Britain's Prince William, Catherine Duchess of Cambridge celebrate World Mental Health Day Britain's Prince William, Duke of Cambridge, Catherine Duchess of Cambridge and Prince Harry celebrate World Mental Health Day at Buckingham Palace in London, Oct. 10, 2017. Heathcliff O'Malley/Reuters

Duchess Kate twists up a pretzel in Germany Britain's Prince William and Kate, the Duchess of Cambridge, share a laugh with Andreas Goebes, right, of the bakers guild Heidelberg as they form pastry to pretzels during a visit at the market in the historic center of the southern German town of Heidelberg, July 20, 2017. Thomas Kienzle/AP

Duchess Kate and Prince William visit Germany Britain's Prince William, right, and his wife Kate, the Duchess of Cambridge, left, arrive at German Cancer Research Center in Heidelberg, Germany, July 20, 2017. Marijan Murat/dpa/AP

Duchess Kate gets into the spirit at Wimbledon The Duchess of Cambridge watches Andy Murray beat Alexander Bublik on Day one of the 2017 Wimbledon Tennis Championships, July 3, 2017, London. Andrew Parsons/i-Images/Polaris

Kate, Duchess of Cambridge, takes in Wimbledon Catherine, Duchess of Cambridge, Patron of the All England Lawn Tennis and Croquet Club (AELTC) on day one of the Wimbledon Championships at The All England Lawn Tennis and Croquet Club, Wimbledon, on July 3, 2017 in London. Gareth Fuller/WPA Pool/Getty Images

The Countess of Wessex, Sophie, accidentally falls onto Kate, Duchess of Cambridge, at Ascot Sophie, Countess of Wessex, loses her balance and falls on to Catherine, Duchess of Cambridge, as the carriages pull away ahead of the first day of the Royal Ascot 2017, June 20, 2017, in Ascot, England. Jason Dawson/Nunn Syndication/Polaris

The royal family steps out in London Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge, Queen Elizabeth II, Princess Anne, Princess Royal, Prince Phillip, Duke of Edinburgh and Princess Beatrice attend a garden party at Buckingham Palace, May 16, 2017, in London. Victoria Jones/WPA Pool/Getty Images

Duchess Kate steps out in Luxembourg Catherine, Duchess of Cambridge departs the Grand Duke Jean Museum of Modern Art where she viewed exhibitions by British artists Sir Tony Cragg and Darren Almond, May 11, 2017, in Luxembourg. Samir Hussein/WireImage via Getty Images

Duchess Kate steps out in Luxembourg A young boy reacts after he is handed a bouquet of flowers to Britain's Catherine, the Duchess of Cambridge in Luxembourg, May 11, 2017. Toby Melville/Reuters

Duchess Kate feeds a lamb Catherine, Duchess of Cambridge feeds a lamb as she visits "Farms for City Children" at Wick Court farm in Arlingham, Gloucester, May 3, 2017. She visited to see the charity work giving young people from inner cities the chance to spend a week on a real working farm. Neil Munns/EPA

Prince William, Duchess Kate and Prince Harry step out in England Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Harry attend the official opening of The Global Academy in support of Heads Together, April 20, 2017, in Hayes, England. Max Mumby/Indigo/Getty Images

Prince William and Duchess Kate attend Easter Sunday service Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge attend Easter Sunday service at Windsor Castle in Windsor, England, April 16, 2017. Alan Davidson/SilverHub/REX/Shutterstock

Duchess Kate takes in a play in London Catherine, Duchess of Cambridge, is presented with tap shoes during the Opening Night Royal Gala performance of "42nd Street" in aid of the East Anglia Children's Hospice at the Theatre Royal Drury Lane, April 4, 2017, in London. Dave Benett/Getty Images

Duchess Kate attends a gala in London Catherine, Duchess of Cambridge, arrives at the 2017 Portrait Gala at the National Portrait Gallery in London, March 28, 2017. Stephen Lock/i-Images/Polaris

Duchess Kate celebrates St. Patrick's Day Catherine, Duchess of Cambridge, at Cavalry Barracks, Hounslow, during the Irish Guards St. Patrick's Day Parade, in London, March 17, 2017. Rupert Hartley/REX/Shutterstock

Duchess Kate visits a hospital Catherine, Duchess of Cambridge visits the Ronald McDonald House Evelina London, Feb. 28, 2017, in London. Danny Martindale/WireImage/Getty Images

Duchess Kate met with children at her new charity Catherine, Duchess of Cambridge visits MIST, a child and adolescent mental health project, Feb. 22, 2017 in Pontypool, Wales. WireImage

Prince William and Duchess Kate Attend the BAFTAs Britain's Prince William, Duke of Cambridge (R) and Britain's Catherine, Duchess of Cambridge arrive to attend the BAFTA British Academy Film Awards at the Royal Albert Hall in London, Feb. 12, 2017. Daniel Leal-Olivas/AFP/Getty Images

Duchess Kate Visits Parenting Center in London Catherine, Duchess of Cambridge arrives for a visit to the CBUK Stratford, Jan. 11, 2017, in London, England. Mark Cuthbert/UK Pres via Getty Images

Duchess Kate and Prince William Take Their Children to Church Prince William, the Duke of Cambridge (R), his wife Catherine, The Duchess of Cambridge (L), Prince George (2nd R) and Princess Charlotte arrive to attend the morning Christmas Day service at St Mark's Church in Englefield, near Bucklebury in southern England, Dec. 25, 2016. Andrew Matthews/Pool/Reuters

The Royal Family Attend the Mix Christmas Party Prince Harry, Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive to attend a Christmas party for volunteers at The Mix youth service, Dec. 19, 2016, in London, England. Chris Jackson/Getty Images

Duchess Kate Attends Cub Scout Meeting Catherine, Duchess of Cambridge reads the Scouts promise during a Cub Scout Pack meeting with cubs in Kings Lynn, England, to celebrate 100 years of Cubs. Ben Stansall/WPA Rota/Nunn Syndication/Polaris

Catherine, The Duchess of Cambridge, attend's a special Cub Scout Pack meeting with Cubs from the Kings Lynn District to celebrate 100 years of Cubs. i-Images, PacificCoastNews

Princess Kate Wears Florals to a Tea Party Kate, the Duchess of Cambridge arrives for a children's tea party at the Natural History Museum to celebrate Dippy the Diplodocus, who has stood in Hintze Hall for over a century, in London, Nov. 22, 2016. Yui Mok/AP Photo

Princess Kate Shows Support for Veterans The Duchess of Cambridge attends the Remembrance Sunday service at The Cenotaph in London, Nov. 13, 2016. Stephen Lock/i-Images / Polaris

Princess Kate Sports a Blue Coat Britain's Duchess of Cambridge waves as she leaves after a visit to the Nelson Trust Women's Center in Gloucester, England, Nov. 4, 2016. Richard Pohler/Pool/AFP/Getty Images

Duchess Kate Stuns in White at Gala Britain's Kate, the Duchess of Cambridge, arrives at Working Titles Office to see "A Street Cat Named Bob" in London, Nov. 3, 2016. The Duchess is attending in aid of Patron of Action on Addiction. Alastair Grant/AP Photo

Duchess Kate Steps Out in Manchester Catherine Duchess of Cambridge is seen at The National Football Museum in Manchester, Oct. 14, 2016. Tim Rooke/REX/Shutterstock

Catherine, Duchess of Cambridge visits Bouwkeet, the social Makerspace of Bospolder-Tussendijken on Oct. 11, 2016 in The Hague, Netherlands. Samir Hussein/Getty Images

Duchess Kate Visits the Netherlands Kate, the Duchess of Cambridge, is greeted by Dutch King Willem-Alexander upon her arrival in The Hague, Netherlands, Oct. 11, 2016. Peter Dejong/AP Photo

Duchess Kate Steps Out in London Catherine Duchess of Cambridge celebrates World Mental Health Day with a special Heads Together event at County Hall and The London Eye on the Southbank, London, Oct. 10, 2016. Tim Rooke/REX/Shutterstock

Duchess Kate Smiles in Fabulous Printed Dress Catherine, Duchess of Cambridge arrives by Sea Plane in Vancouver, Sept. 25, 2016 in Vancouver, Canada. Samir Hussein/Getty Images

Princess Kate Smiles After Meeting With Young People Catherine, Duchess of Cambridge leaves Stewards Academy, Sept. 16, 2016, in Harlow, England. Getty Images

Duchess Kate Sports a Navy Blazer Catherine, Duchess of Cambridge is seen at Tresco Abbey Gardens during a visit to Cornwall, Sept. 2, 2016, in Tresco, England. GC Images/Getty Images

William and Kate Step Out in Cornwall Britain's Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge, begin their visit to Cornwall in Truro, Sept. 1, 2016. FameFlynetUK/FameFlynet Pictures

Duchess Kate Steps Out in Red Dress Catherine, Duchess of Cambridge is seen during a visit to the YoungMinds mental health charity helpline, partner of the Heads Together mental health charity, Aug. 25, 2016, in London. Danny Martindale/WireImage/Getty Images

The Duke and Duchess of Cambridge arrive at Bute Mills in Luton, where they will tour the facilities of national charity Youthscape. PA Wire/Press Association Images

Princess Kate Attends the America's Cup World Series Catherine, Duchess of Cambridge visits Land Rover BAR boat shed at the America's Cup World Series, July 24, 2016, in Portsmouth, England. Henry Browne/Getty Images

Duchess Kate Cheers on Andy Murray at Wimbledon Catherine, Duchess of Cambridge attends the Men's Final of the Wimbledon Tennis Championships between Milos Raonic and Andy Murray at Wimbledon, July 10, 2016, in London. Karwai Tang/WireImage

Duchess Kate Attends an Air Show With Prince George Catherine, Duchess of Cambridge and Prince George of Cambridge attend the The Royal International Air Tattoo at RAF Fairford, July 8, 2016, in Fairford, England. Samir Hussein/WireImage

Duchess Kate Attends Wimbledon Catherine, Duchess of Cambridge, stands in the royal box watching the ladies semifinals at Wimbledon Tennis Championships in London, July 7, 2016. Andrew Parsons/Polaris

Duchess Kate Stuns in a Cream Gown Catherine, Duchess of Cambridge arrives to present the Art Fund Museum of the Year 2016 prize at a dinner hosted at the Natural History Museum, July 6, 2016, in London. Getty Images

Duchess Kate Attends a Vigil With Prince William and Prince Harry Prince Harry, Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge, take part in a vigil at Thiepval Memorial to the Missing of the Somme during Somme Centenary Commemorations and view the battlefields of the Somme in France, June 30, 2016. Splash News

Duchess Kate Attends a Vigil With Prince William and Prince Harry Prince Harry, Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge, take part in a vigil at Thiepval Memorial to the Missing of the Somme during Somme Centenary Commemorations and view the battlefields of the Somme from the top of the Thiepval Monument in France, June 30, 2016. Splash News

Duchess Kate Stuns in a Dress She First Wore in 2011 Catherine, Duchess of Cambridge attends a gala dinner in support of East Anglia's Children's Hospices' nook appeal at Houghton Hall, June 22, 2016, in King's Lynn, England. Stephen Pond/Getty Images

Britain's Kate Duchess of Cambridge signs a book of condolence for the Orlando nightclub shooting victims at the US Embassy in London, while Prince William looks on, June 14, 2016. Philip Toscano/AP Photo

The Royal Family Greets Well-Wishers at Buckingham Palace (L-R) Prince Charles, Prince of Wales, Catherine, Duchess of Cambridge, Princess Charlotte, Prince George, Prince William, Duke of Cambridge, Prince Harry, Queen Elizabeth II and Prince Philip, Duke of Edinburgh stand on the balcony of Buckingham Palace during the Trooping the Color, this year marking the Queen's 90th birthday at The Mall, June 11, 2016 in London. Ben A. Pruchnie/Getty Images

Duchess Kate Celebrates the Queen's 90th Catherine, Duchess of Cambridge attends a lunch after the National Service of Thanksgiving as part of the 90th birthday celebrations for The Queen at The Guildhall on June 10, 2016 in London. Jeff Spicer/Getty Images

Duchess Kate Steps Out in a Cut-Out Dress Duchess Kate attends SportsAid's 40th anniversary dinner in London, June 9, 2016. On arrival, The Duchess will met SportsAid ambassadors and young athletes who will be competing in the Rio 2016 Olympics at a pre-dinner reception, as well as some of the charity's key supporters. Eddie Mulholland-WPA Pool/Getty Images

Duchess Kate and Prince William Attend a Garden Party Prince William, Duke of Cambridge and Catherine, Duchess of Cambridge arrive to greet guests attending a garden party at Buckingham Palace, May 24, 2016, in London. Dan Kitwood/WPA Pool/Getty Images

Duchess Kate Middleton Looks Lovely in Green Catherine, Duchess of Cambridge attends Chelsea Flower Show press day at Royal Hospital Chelsea, May 23, 2016 in London. Mark Cuthbert/UK Press via Getty Images

Duchess Kate Middleton Looks Regal in White Catherine, Duchess of Cambridge, patron of the 1851 Trust, arrives at Land Rover BAR, May 20, 2016 in Portsmouth, England. Chris Jackson/Getty Images

Catherine, Duchess of Cambridge joins the Land Rover BAR team on board their training boat, as they run a training circuit on the Solent, May 20, 2016, in Portsmouth, England. Mark Cuthbert/UK Press via Getty Images

Catherine, Duchess of Cambridge joins the Land Rover BAR team on board their training boat, as they run a training circuit on the Solent, May 20, 2016, in Portsmouth, England. Mark Cuthbert/UK Press via Getty Images

Duchess Kate and Princes William and Harry Launch Their Health Initiative Prince William and Catherine, Duke and Duchess of Cambridge, and Prince Harry attend the launch of their Heads Together campaign to eliminate stigma on mental health at the Queen Elizabeth Olympic Park in London. Robin Nunn/Nunn Syndication/Polaris

Duchess Kate Attends Her Portrait Unveiling Catherine, Duchess of Cambridge is seen leaving the "Vogue 100: A Century Of Style" exhibition at National Portrait Gallery, May 4, 2016, in London. Danny Martindale/WireImage/Getty Images

Duchess Kate Plays Cricket in Wedges Catherine Duchess of Cambridge plays during a visit to meet children from Magic Bus, Childline and Doorstep, three non-governmental organizations, at Mumbai's iconic recreation ground, the Oval Maidan, during the royal visit to India and Bhutan on April 10, 2016 in Mumbai, India. Tim Rooke/REX/Shutterstock

Prince William and Duchess Kate Attend a Bollywood Bash Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge arrive for a Bollywood Inspired Charity Gala at the Taj Mahal Palace Hotel during the royal visit to India and Bhutan on April 10, 2016 in Mumbai, India. Samir Hussein/Getty images

Prince William and Duchess Kate Step Out Ahead of Their India Trip Prince William, Duke of Cambridge and Princess Catherine, Duchess of Cambridge attend a reception ahead of their tour of India and Bhutan at Kensington Palace, April 6, 2016, in London. WPA Pool/Getty Images

Duchess Kate Makes Steps Out in Blue for a Charity Catherine, Duchess of Cambridge opens the new EACH Charity Shop, March 18, 2016, in Holt, Norfolk. Mark Cuthbert/UK Press via Getty Images

Duchess Kate and Princes William and Harry Head to Westminster Abbey Britain's Prince William, Duke of Cambridge, his wife Catherine, Duchess of Cambridge, and Prince Harry arrive to attend a Commonwealth Service at Westminster Abbey in central London, March 14, 2016. Queen Elizabeth II has been Head of the Commonwealth throughout her 60 year reign. Organised by the Royal Commonwealth Society, the Service is the largest annual inter-faith gathering in the United Kingdom. Leon Neal/AFP/Getty Images

Kate Middleton Steps Out in London Kate Middleton, Duchess of Cambridge visit the mentoring program of the XLP project at London Wall, which supports young people who are facing emotional, behavioral and relational challenges in London, March 11, 2016. James Whatling/Splash News

Kate Middleton Visits St Thomas' Hospital Kate Middleton, Duchess of Cambridge listens to a former patient during a visit to St Thomas' Hospital with Prince William, in London, March 10, 2016. Toby Melville /Pool Photo via AP Photo

The Royal Family's Sweet Vacation Photos Catherine, Duchess of Cambridge, Princess Charlotte, Prince George and Prince William, Duke of Cambridge pose as they enjoy a short private break skiing in the French Alps, France, March 3, 2016. John Stillwell/PA/EPA

The Royal Family's Sweet Vacation Photos Prince William, Duke of Cambridge cuddles his daughter Princess Charlotte of Cambridge as he and is family enjoy a short private break skiing in the French Alps, France, March 3, 2016. John Stillwell/PA/EPA

The Royal Family's Sweet Vacation Photos Prince William, Duke of Cambridge, Prince George, Catherine, Duchess of Cambridge and Princess Charlotte pose for pictures as they enjoy a short private break skiing in the French Alps, France, March 3, 2016. John Stillwell/PA/EPA

The Royal Family's Sweet Vacation Photos Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge laugh after she threw a snowball at him during a short private break skiing in the French Alps, France, March 3, 2016. John Stillwell/PA/EPA