The Duchess of Sussex is in labour and is expected to give birth to her baby within hours.
Meghan, 37, was intending to give birth at her home at Frogmore Cottage, Windsor, where she lives with Prince Harry.
But Harry and Meghan have decided to keep details of the birth secret therefore it is unknown if she is in hospital or at home - her preferred choice.
Proud father Prince Harry, Duke of Sussex is at Meghan’s side and is expected to be present at the birth.
A Palace statement today read: "The Duchess went into labour in the early hours of this morning. The Duke of Sussex was by Her Royal Highnesses’ side. An announcement will be made soon."
The next news Buckingham Palace will announce is when the baby is born and the sex and weight of the child, who will be seventh in line to the throne.
The Queen, Duke of Edinburgh, Prince of Wales and Duchess of Cornwall, Duke and Duchess of Cambridge and 'members of both families' have been informed and will be told of any developments.
Prince Charles and his wife Camilla, Duchess of Cornwall, had been expected to visit the couple once the new baby is born.
But they are due to fly to Germany on an important official visit.
The baby’s position in the line of succession was assured as 7th irrespective of sex due to the change in the primogeniture.
The child was tipped to be born in late April or early May and is thought to be a few days overdue.
It will be The Queen’s decision whether the baby will be a prince of princess, although Harry and Meghan of course will have an input.
A royal decree issued by King George V in 1917 limits the number of grand royal titles in a way that could make Harry and Meghan's baby known as a Lord or a Lady as the child of a Duke rather than as a prince or princess.
The Queen issued a new Letters Patent on December 31, 2012 declaring that all of the Duke and Duchess of Cambridge’s children will have the title of Royal Highness and be styled Princes and Princesses.
The document states: "The Queen has been pleased by Letters Patent under the Great Seal of the Realm dated 31 December 2012 to declare that all the children of the eldest son of The Prince of Wales should have and enjoy the style, title and attribute of Royal Highness with the titular dignity of Prince or Princess prefixed to their Christian names or with such other titles of honour."
The Queen’s Letters Patent revised King George V’s 1917 decree that only the eldest son of the Prince of Wales’s eldest son was entitled to be styled His Royal Highness and a Prince.
According to this document, the daughters and younger sons of the Prince of Wales’s eldest son were to be styled as children of a Duke. These ducal titles would change to royal titles once the Prince of Wales succeeded to the throne.
The Queen’s decree ensured that if the Duke and Duchess of Cambridge’s eldest child is a daughter, she will be styled a Princess rather than a Lady.
She could intervene again in that case and do the same for Harry and Meghan's offspring, but Her Majesty’s position on that subject has not been made public.
It is also possible that Harry and Meghan could decide they don't want the special designation for the baby, in order to give their child a more normal upbringing.
The odds on the seventh in line to the throne’s name have been changing with Diana at 6-1, which would pay tribute to Prince Harry's late mother, Diana, Princess of Wales as the favourite.
This is followed by Philip in second place at 10-1.
The Royal Collection has already released a "Royal Baby Bear 2019".
The new limited edition cream bear, which costs £125, has been handmade by traditional Shropshire-based teddy bear makers Merrythought especially for the Royal Collection.
Only 100 of the 19cm-tall toys - made using alpaca fleece with 100% cotton back and pure silk - are available to buy.
The bear, finished with a cream bow around its neck, has an embroidered golden crown and "2019" on one of its feet.
Baby Sussex will be a product of two cultures: its father a prince who is a symbol of Britain; its mother quintessentially American - a self-made TV star with a white father and an African American mother.
The child is unlikely to ever become king or queen, but the presence of a half-American child who may choose to hold dual nationality could shake up the royal family, just as the arrival of Meghan has had a modernizing effect on the stately but sometimes stodgy House of Windsor.
"It's quite possible the child will have a lot of American influence," royal commentator Hugo Vickers said. "The royal family is not totally unused to that kind of thing.
Children have been born with Greek mothers or German mothers in the past, obviously, but Meghan is the first American mother so close in the royal family."
