The Duchess of Cambridge will present the BBC's Sports Personality of the Year award and the lifetime achievement honour tonight, St. James's Palace said.
Catherine has not been seen in public since leaving the King Edward VII's Hospital in London on December 6.
She received three days of treatment for a condition known as hyperemesis gravidarum, which leaves expectant mothers so ill they cannot keep food or liquids down.
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The singer had been tweeting in support of migrants when she was bombarded with abusive messages.
Ministers are reportedly considering plans in a bid to lower inward migration.
In a tweet on Saturday, the US president didn't give a reason for his absence but said he wished"everyone well and have a great evening".