As early as Monday, the signs were not looking good. The National Zoo's female giant panda, Mei Xiang, was exhibiting some behaviors of pregnancy, but not all of them. The ultrasound scans of her uterus were inconclusive. And the level of certain hormones in her body were saying that her annual pregnancy cycle was over. Plus, there was no cub. The zoo announced Wednesday that, taking all factors into consideration, their panda was once again not pregnant. The conclusion was reached, the zoo said, after experts studied the array of physical, behavioral and chemical clues. 'Based on current hormone analyses, and not having seen a fetus during the ultrasound exams, Zoo researchers have determined that Mei Xiang experienced a pseudopregnancy,' the zoo said in a statement. The zoo had placed the panda on 24-hour pregnancy watch Friday, and officials had high hopes that Mei Xiang might be pregnant. She was artificially inseminated twice in January. 'This is very disappointing news, as you can imagine,' Dr. Janine Brown, head of the zoo's endocrinology lab, said in an e-mail. 'Everyone puts their heart and soul into the reproductive management of these and other species,' she said. 'We had no reason to believe Mei's last artificial insemination would not be successful, but as so often happens, nature had other ideas.' Mei Xiang has had numerous pseudo-pregnancies in the past and in a decade has produced one cub, Tai Shan. The disappointment comes after the departure in February of the zoo's giant panda favorite, Tai Shan, who was born there in 2005. Tai Shan was sent to join a breeding program in China. In addition, the zoo faces the possibility that Mei Xiang and her mate, Tian Tian, may also soon depart. The adult giant pandas are here on a 10-year lease from China that expires in December. 