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Three days after she gave birth to twins, giant-panda mother Mei Xiang seems to be throwing a wrench into the National Zoo’s efforts to keep both cubs healthy, during a “high-risk period” for them.

The National Zoo says in a press release issued this afternoon that Mei hasn’t given up the larger of the two cubs since 2 p.m. Monday, preventing the panda team from swapping the twins, as is protocol. The larger cub, weighing 138 grams at birth, seems to be doing well; the smaller one, who was born weighing 86 grams, has experienced “fluctuating weight,” thus causing concerns.

“The panda team is caring for the smaller cub and will continue efforts to swap the cubs about every four hours,” the release says. “However, because the smaller cub has been away from Mei, the panda team is now managing it more intensely.”

Zoo employees will keep providing the smaller twin with fluids and nutrients through bottle- and tube-feeding, although they’re worried it might aspirate its food. To combat any infections that might arise from food “going down the wrong pipe,” the panda team is giving the cub antibiotics.

“The cub is urinating and defecating well,” the National Zoo’s press release explains. “The veterinarians have not seen any sign of respiratory distress.”

Today’s developments follow a “challenging night” for the panda family on Sunday, during which Mei would also not give up the larger of the two cubs. Stay tuned for more #PandaStory.

Photos by Heather Roberts, National Zoo