Updated | Princess Kate expecting second child

Two weeks ahead of her visit to Malta, it has been revealed that the Duchess of Cambridge is pregnant with her second child

The duchess is being treated by doctors at Kensington Palace for acute morning sickness, a condition called Hyperemis Gravidarum. She was hospitalized early in her first pregnancy because of the condition, which can cause severe nausea, vomiting and dehydration.

The Duchess of Cambridge was expected to visit Malta on Saturday 20 and Sunday 21 September to represent Queen Elizabeth II on the occasion of the 50th anniversary of Malta's Independence, however her pregnancy has put her presence in Malta in doubt.

The Office of the Prime Minister congratulated the Duchess and in a statement issued this afternoon government said that it was in contact with the British government and the Royal family over the visit to Malta.

However, government said it was too early to determine whether the Duchess will go ahead with her visit, adding that the decision will be taken at a later date.

Kensington Palace said the Queen and members of both families were delighted with the news.

The palace said that - as when she was pregnant with Prince George - the duchess was suffering from very acute morning sickness and was being treated by doctors at Kensington Palace.

The couple's second child will become fourth in line to the throne, moving Prince Harry further down the line of succession.

Clarence House said: "Their Royal Highnesses the Duke and Duchess of Cambridge are very pleased to announce that the Duchess of Cambridge is expecting their second child."

The duchess's morning sickness meant that she would no longer accompany Prince William on their planned engagement in Oxford on Monday, Clarence House said.

Catherine had been due to join William in formally opening a £21m China study centre at Oxford University.

The sickness - called hyperemesis gravidarum - is a condition that may require supplementary hydration, medication and nutrients.

The duchess had been due to carry out her first solo overseas tour in Malta later this month.

The baby announcement came two months after the couple's first child, Prince George, had his first birthday.

Unlike when she was pregnant with George, the duchess is being treated at Kensington Palace and not at a hospital.