A giant panda gave birth Friday afternoon at the Smithsonian National Zoo, marking a successful case of breeding the endangered species in captivity, the zoo announced on their website.While staff monitored her condition, the panda, named Mei Xiang, successfully gave birth and began cradling the newborn cub. Its sex has yet to be determined, and will be verified at a later date. It is exceedingly difficult for pandas to give birth, as the females are only able to become pregnant during a small window of around 24-72 hours in a single year. As such, they must always be closely monitored in order to determine the proper time to go ahead with artificial insemination. There are signs for this, which include detecting ovulation via hormone analysis, but there are also several behavioral cues.Mei Xiang was inseminated in March, but the pregnancy wasn't confirmed until August.The successful birth is a landmark occasion for multiple reasons. First among these milestones, is the fact that this was the first successful pregnancy and birth through artificial insemination in the US. But arguably even more notable is the age. At 22, Mei Xiang is the oldest panda in the US, and is the second oldest panda to have ever been documented giving birth, the Smithsonian reported. Though pandas can breed into their 20s, the advanced age still made the pregnancy and birth even more unlikely.“Giant pandas are an international symbol of endangered wildlife and hope, and with the birth of this precious cub we are thrilled to offer the world a much-needed moment of pure joy,” explained Steve Monfort, John and Adrienne Mars director of the Smithsonian’s National Zoo and Conservation Biology Institute.“Because Mei Xiang is of advanced maternal age, we knew the chances of her having a cub were slim. However, we wanted to give her one more opportunity to contribute to her species’ survival. I am incredibly proud of our animal care and science teams, whose expertise in giant panda behavior was critical to this conservation success.”For more on Mei Xiang and her newborn cub, the zoo will post updates to their social media accounts using the hashtag #PandaStory.