Photo by Dan Dan The Binary Man.

Although Mei Xiang has declined to participate in ultrasounds for a few weeks, she acquiesced this morning. And when surprised veterinarians took a look at the images on the screen, they detected what appears to be a fetus of about four centimeters.

Mei Xiang was artificially inseminated with sperm from Hui Hui, a panda living in China, as well as the National Zoo’s Tian Tian back in April. The zoo announced on Aug. 10 that Mei Xiang’s hormones had definitely been rising for a few weeks, which either means another butter stick-sized baby or a pseudopregnancy that would end within 30 to 50 days. The only way to tell for sure is by detecting the tiny fetus on an ultrasound.

Although there is a significant chance that she could still resorb the fetus or have a miscarriage, zookeepers are “cautiously optimistic.” Based on its size, Mei Xiang could give birth as early as next week, or early September.

“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,” said Dennis Kelly, director of the Smithsonian’s National Zoo.

The David M. Rubenstein Family Giant Panda Habitat will be closed to provide some peace and quiet for Mei Xiang, though Tian Tian and Bao Bao will still be on view in their outdoor enclosures.

Courtesy of the National Zoo.