WASHINGTON, Aug. 19 (UPI) -- Washington National Zoo's female giant panda Mei Xiang is likely pregnant, veterinarians said Wednesday after detecting what they believe to be a developing fetus.
Officials at the zoo performed an ultrasound on the panda Wednesday morning and found what is possibly a fetus about four centimeters in size. Based on the size, Mei Xiang could give birth as soon as next week or early September.
Panda pregnancies are difficult to detect due to the animal mimicking the behaviors and hormones associated with being pregnant. The only concrete way of confirming a pregnancy is to see a fetus on an ultrasound, but a giant panda fetus does not start developing until the final weeks of gestation, the zoo said.
The zoo has noticed Mei Xiang is nest-building and spending more time resting in her den.
Veterinarians inseminated Mei Xiang once on April 26 and again April 27 using semen collected from two male giant pandas -- Hui Hui from the China Conservation and Research Center for the Giant Panda in Wolong, China, and Tian Tian from the National Zoo.
If a baby panda is born, the zoo will confirm the father through a DNA test.
"Today, we are cautiously optimistic," said Dennis Kelly, director of the Smithsonian's National Zoo. "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."
Mei Xiang has previously given birth to two surviving cubs: Tai Shan in 2005 and Bao Bao in 2013. The older cub now lives in China and Bao Bao, who turns 2 on Sunday, shares a habitat with her mother.