The cancellation was confirmed in a tweet by Clarence House this morning, which also said that Prince William will be visiting in his wife's place.
The tweet read: "The Duchess of Cambridge will no longer visit Malta this weekend. The Duke of Cambridge will undertake the visit instead #RoyalVisitMalta."
The Duchess of Cambridge will no longer visit Malta this weekend. The Duke of Cambridge will undertake the visit instead #RoyalVisitMalta
Another tweet read: "HRH continues to suffer from Hyperemesis Gravidarum. The decision was taken on the advice of doctors #RoyalVisitMalta."
HRH continues to suffer from Hyperemesis Gravidarum. The decision was taken on the advice of doctors #RoyalVisitMalta
The duchess was due to fly to Malta to celebrate the former British colony's 50th anniversary of independence on a two-day tour from 20 to 21 September.
Details of her tour itinerary were released in August and include a meet and greet with the Prime Minister Joseph Muscat and his wife as well as a series of military-themed presentations, a visit to the National Library and Independence Day celebrations.
William will now carry out those duties instead, and is reportedly happy to, with Clarence House tweeting:
The Duke of Cambridge is honoured to represent The Queen on the visit, which commemorates the 50th anniversary of Malta's Independence
Since announcing her second pregnancy in early September, Kate has suffered with severe morning sickness, and also had to pull out of the opening ceremony of the Invictus Games.
Here's hoping she feels better soon.
Missing Duchess Kate fashion? Don't worry, we have a gallery jam-packed with red carpet pictures for you to peruse...
More? Oh, go on then: