The Prince and Princess of Wales released a photo of Catherine with their three children George, Charlotte, and Louis on Sunday to mark Mother's Day in the U.K.
The image was heavily scrutinised online, with social media users claiming that it had been digitally manipulated, and several news agencies subsequently pulled the photo over questions about its authenticity.
Catherine, 42, admitted she edited the snap in a statement on the couple's social media accounts on Monday.
"Like many amateur photographers, I do occasionally experiment with editing," she wrote. "I wanted to express my apologies for any confusion the family photograph we shared yesterday caused. I hope everyone celebrating had a very happy Mother’s Day. C."
The photo, taken by Prince William, marked the first official image to be released of Catherine since she underwent abdominal surgery in January. She has been recovering in private ever since and is not expected to return to public duties until after Easter.
She captioned the post, "Thank you for your kind wishes and continued support over the last two months. Wishing everyone a Happy Mother's Day. C."
Earlier this month, Catherine was spotted for the first time since her surgery; she was photographed in the passenger seat of her mum Carole Middleton's car near Windsor Castle.
