US panda Mei Xiang's cub 'doing well' but twin is stillborn Mei Xiang gives birth to a cub on Friday night at the National Zoo in Washington. The next night she delivered its stillborn twin. A panda at Washington's National Zoo that has been tending to her squealing newborn cub has also given birth to a stillborn cub that wasn't fully formed, a zoo official says. Mei Xiang gave birth to the motionless cub on Saturday night after giving birth to its live twin the night before, zoo spokeswoman Pamela Baker-Masson said. The mother groomed her stillborn cub for 17 minutes before letting it fall to the floor, she said. The panda still has not let zoo staff get close enough to get a good look at her live cub but it was squealing and appeared to be doing well, Baker-Masson said. The zoo began performing a necropsy on the stillborn cub late on Saturday to find out why it stopped developing and died in-utero, she said. When caretakers do get to check out the live cub they will try to listen to its heart and lungs, record its weight and collect a DNA sample. Brandie Smith, the zoo's curator of mammals, said she and others were "cautiously optimistic" about the cub's health. She compared the planned exam to a race car pit stop: a fast and highly choreographed checkup before reuniting mother and cub. The live cub was the 15-year-old panda's third. Mei Xiang gave birth to a cub last year that died after just six days. Its lungs had not fully developed and likely were not sending enough oxygen to its liver. Mei Xiang's first cub, a male named Tai Shan, was born in 2005. Zoo staff have made several changes in preparation for the new cub. Mei Xiang's den was altered to allow keepers to get closer and the zoo invited a panda expert from China who specialises in newborns to help. Two of the zoo's panda keepers also recently spent time in China learning more about examining newborns.