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The countdown is on: Meghan and Harry’s first baby is expected any day now. The couple has just launched a joint Instagram account, sparking fevered speculation that a big announcement is on the way.

The news was delivered less than an hour after Buckingham Palace announced that the Duchess of Sussex had gone into labor early on Monday with Prince Harry by her side.

“I’m very excited to announce that Meghan and myself had a baby boy earlier this morning, a very healthy boy,” a beaming Prince Harry told members of the media at Windsor Castle.

“Mother and baby are doing incredibly well. It’s been the most amazing experience I could ever have possibly imagined.”

Here’s what we know so far – and what the world is waiting to find out – about the newest addition to the royal family.

When did Meghan announce her pregnancy?

In October 2018, just five months after their wedding, Harry and Meghan touched down in Australia for their first overseas tour as a married couple.

The Duke and Duchess of Sussex announced they were expecting a baby during their Australian tour.

What was already set to be a hectic visit turned into a royal frenzy when news that the couple were expecting broke as they arrived in Sydney at the start of their 16-day tour of Australia, New Zealand, Fiji and Tonga.

When is the baby due?

Kensington Palace officials have been tight-lipped about the Duchess of Sussex’s exact due date, other than to say that Meghan and Harry’s first baby is due in the spring of 2019.

But at various royal engagements since the original announcement, Meghan is said to have told members of the public the baby is due to arrive around the end of April or the beginning of May.

Meghan told well-wishers that the baby was due at the end of April or beginning of May.

When the couple launched a joint Instagram account on April 2, fevered speculation followed that a big announcement was imminent.

But the public had to wait more than a month for the Instagram post on May 6 announcing: “It’s a BOY!”

“We are pleased to announce that Their Royal Highnesses The Duke and Duchess of Sussex welcomed their firstborn child in the early morning on May 6th, 2019. Their Royal Highnesses’ son weighs 7lbs. 3oz,” Sussex Royal wrote.

Prince Harry told the media at Windsor Castle on Monday that his son was “a little bit overdue,” giving the couple “a little bit of time to think about” names.

Where will Meghan give birth?

With just days or weeks to go, it is still unclear where the new royal baby will make his or her entrance into the world.

In recent years, the Lindo Wing at London’s St. Mary’s Hospital has become the de facto maternity ward for royal births.

Crowds greet Prince William and the Duchess of Cambridge at the Lindo Wing of St. Mary's Hospital.

Catherine, the Duchess of Cambridge, gave birth to her three children – Prince George, Princess Charlotte and Prince Louis – at the hospital.

It is also where Harry and his brother Prince William were born.

Diana and Charles leave the Lindo Wing after the birth of their first son, Prince William, in July 1982.

But in recent weeks, speculation mounted that Meghan would chose a home birth. This would be more in keeping with the couple’s frequent requests for privacy – a plea they have made since they began dating three years ago, and repeated in the weeks leading up to the birth of their son.

What happens after Meghan gives birth?

Once the baby is born, Queen Elizabeth II, British Prime Minister Theresa May and the Governor General of each Commonwealth nation will be informed, along with the rest of the royals and Meghan’s family in the United States.

Following the birth, an official notice will be signed by Meghan’s doctors, confirming the newborn’s gender, weight and time of birth.

A notice is placed on an easel outside Buckingham Palace to announce the birth of a royal baby.

This notice will be taken to Buckingham Palace, under police guard, where it will be framed and placed on an easel in the palace forecourt, for members of the public to read.

When will the public get to see the baby for the first time?

This is up to Meghan and Harry, and will likely depend at least in part on where the royal baby makes his or her entrance.

Harry hinted to gathered media on Monday that the world would have its first glimpse of his son on Wednesday.

The couple have previously said they “look forward to sharing the exciting news with everyone once they have had an opportunity to celebrate privately as a new family.”

The Duke and Duchess of Cambridge leave the Lindo Wing with their son Prince Louis.

What will the baby be called?

It could take anything up to 10 days after the birth for the baby’s name to be announced.

Speaking to Reuters on Monday, Harry said they were “still thinking about names.”

Until then, speculation will be rife.

Tradition plays a huge role when choosing a royal name.

Albert, for example, would be a reference to Queen Victoria’s husband, Prince Albert and also to Queen Elizabeth II’s father, King George VI, who was known as Albert until his accession to the throne. And, of course, Diana would be a nod to Harry and William’s mother, who was killed in a car crash in Paris in 1997.

But the couple could opt to skip tradition altogether, as Queen Elizabeth’s granddaughter Zara Phillips did when she chose to name her daughters Mia Grace and Lena Elizabeth.

Meghan’s American background might even influence the couple’s choice of name for their child.

What surname will the baby have?

Royal babies are given a lot of names – Harry’s full name, for example, is Henry Charles Albert David. But those titled His or Her Royal Highness don’t, traditionally, have a surname.

When William and Harry were at school and during their later military careers, they used “Wales” – derived from their father’s official title as Prince of Wales.

Harry and Meghan -- the Duke and Duchess of Sussex -- were married at Windsor in May 2018.

As descendants of Queen Elizabeth II and the Duke of Edinburgh, they could also use Windsor, or Mountbatten-Windsor – both of which are relatively new inventions, adopted during World War I to disguise the family’s German origins.

As for Meghan and Harry, their child will likely use Sussex – their assigned dukedom – as a surname, just as William and Catherine’s children use Cambridge at school.

Could the baby be King or Queen?

Meghan and Harry’s child, who will be Queen Elizabeth II’s seventh great-grandchild, will be seventh in line to the throne. He or she will follow Charles, the Prince of Wales – who is currently the next in line, followed by William, his three children and Harry himself.

So, does that mean the baby will be a prince or princess?

Despite being seventh in line to the throne, Meghan and Harry’s baby won’t automatically become a prince or princess.

That’s because in 1917, King George V limited the use of such titles within the British royal family, and the couple’s child will be too far down the line of succession.

However, the Queen could step in to overrule that decree – as she has done with William and Catherine’s younger children, Princess Charlotte and Prince Louis (since he’s third in line to the throne, George was automatically a prince).

Queen Elizabeth II was one of the first to hear news of the birth of Meghan and Harry's son.

Will he or she have dual citizenship?

Meghan and Harry’s child will become the first British-American baby born into the royal family.

The newborn will automatically be a British citizen, but the Duke and Duchess of Sussex will have to report their child’s birth to an American consulate in order for him or her to obtain US citizenship.

Harry and Meghan's child will be born a British citizen; he will also be eligible for US citizenship.

In the case of the royal baby, he or she will be eligible because s/he was born in wedlock abroad to an American citizen who has lived in the US for a period of five years, at least two of which were after the age of 14 – according to the US Department of State.

Why has the world gone wild over Meghan and Harry’s baby?

News of the royal baby was a largely symbolic landmark for the UK’s history books, particularly at a time when Britain’s busy cutting its ties with the European Union, writes Jane Merrick for CNN.

“The new prince or princess will not only have that American heritage, but will also be the first biracial baby in line to the British throne,” she said.

Harry and Meghan's wedding was hailed as a unifying moment for the UK, amid divisions over Brexit.

“Any new baby is a symbol of hope for the future of any family. But these expectations will be made all the heavier for the newest member of the royal family – particularly at a time of uncertainty and upheaval in the UK.”

According to Merrick, Meghan and Harry’s wedding was a “much-needed counterpoint to the climate of fear and hostility over immigration that has become magnified since the Brexit referendum.”