Since Prince George's birth in July, the Duchess of Cambridge has rarely been seen in public as she adjusts to life as a mother.
In September, Prince William and Kate spent their first night away their son to attend a black-tie awards ceremony.
The Duchess had previously made her first surprise public appearance since George's birth when she joined her husband as he started the Anglesey Coastal Ultra Marathon in August.
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Mr Kim has made two recent visits to China.
The study looked at the development of 422 children over the course of eight years.
The president said they will come into force if China refuses to change its practices.