Photo courtesy of the Smithsonian National Zoo

After posting a photo of a positive pregnancy test on Facebook yesterday, the Smithsonian National Zoo had some locals guessing whether they’d soon be able to visit a baby elephant, panda, gorilla, or kid of a zookeeper. Some animal lovers guessed it right—a baby orangutan is on the way, the zoo announced this afternoon.

An endangered 19-year-old Bornean orangutan, Batang, is expected to birth the first baby orangutan to reside at the zoo in 25 years. Zookeepers took viewers behind the scenes in a video today where they conducted a live ultra sound on Batang.

After being taken off birth control, Batang bred with Kyle, another Bornean orangutan—although he had another love interest, zookeepers said earlier this year while speaking about the zoo’s mating procedures.

A regular old human pregnancy test confirmed she was with child in February, according to a release from the zoo. Since then, staffers have watched the fetus develop, which has been “incredibly exciting,” said Meredith Bastian, the zoo’s curator of primates. “We’re making every effort to ensure our efforts come to fruition,” she continued.

Zookeepers are predicting that Batang will birth her first child in mid-September, however, just like any animal pregnancy, complications could occur. The zoo will update its social media outlets periodically about the birth—folks can follow along using the hashtag #Orangutanstory.