(CNN) Meghan, Duchess of Sussex, was in the crowd at Wimbledon on Thursday to watch Serena Williams in her second-round match against Kaja Juvan.

The American was shocked in the first set by the 18-year-old Slovenian but rallied back to take the match 2-6 6-2 6-4.

Meghan Markle appeared to be wearing a necklace adorned with an "A," the first initial of her son Archie's name.

It comes ahead of Archie Harrison Mountbatten-Windsor's christening, which will take place in the Private Chapel at Windsor Castle on Saturday, exactly two months after he was born on May 6.

Williams and the duchess are close friends, having met a few years ago at a charity event. Williams and her husband, Reddit co-founder Alexis Ohanian, attended the former US actor's wedding to Prince Harry last May.