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National Zoo watchers and panda fanatics have cause for celebration today: Giant panda Mei Xiang is believed to be pregnant.

The zoo issued a press release Wednesday afternoon describing the most recent updates to Panda Watch 2015. Mei Xiang responded to zookeepers’ calls this morning, allowing them to perform an ultrasound, after declining to participate in the procedure since Aug. 7 (a favored tradition). The ultrasound revealed what appears to be a fetus four centimeters in length. Although Mei Xiang could give birth as early as next week, the press release cautions that “there is a substantial possibility that [she] could resorb or miscarry a fetus”—the former a biological process scientists don’t fully understand.

“Today, we are cautiously optimistic,” said Dennis Kelly, director of the National Zoo, in a statement. “We want a healthy cub for all the right conservation reasons. I am excited, but I have to say that we were prepared for a cub even before this morning’s ultrasound. Our expert team of keepers, scientists and veterinarians are going to do exactly what they are trained to do and I’ll just ask everyone to remain positive with us.”

Zookeepers will continue to monitor Mei Xiang through panda cams as she exhibits behaviors that are associated with pregnancy or pseduopregnancy: sleeping more, cradling objects, and spending more time in her den. Previously, zoo officials noticed that Mei Xiang’s hormones were rising over the past few weeks, but hormones alone aren’t dispositive of a pregnancy.

Smithsonian scientists artificially inseminated Mei Xiang on April 26 and 27 of this year, using sperm from resident panda Tian Tian and Hui Hui, a giant panda living in China’s Wolong National Nature Reserve. “A cub by Mei Xiang and Hui Hui would be very genetically valuable, helping to preserve the genetic diversity of the panda population in human care,” the National Zoo’s press release explains. “Scientists also used high-quality fresh semen collected from the Zoo’s male giant panda, Tian Tian, for the artificial inseminations. DNA analysis will determine the sire of the cub.”

Mei Xiang, 17, is already the mother of two: Tai Shan, a 10-year-old male, and Bao Bao, a female whose second birthday is on Sunday. To celebrate, Bao Bao will receive a “frozen treat.”

In other panda-related news today: Tai Shan Chinese Restaurant, in Chinatown—which shares a name with Mei Xiang’s first cub, now living in China—will close after 21 years of service on Aug. 29, Eater DC reports. Because you know what they say, after all: When one door closes…

Ultrasound image courtesy of  Smithsonian National Zoological Park