WASHINGTON (AP) — Zoo officials in Washington are hoping to get panda mom Mei Xiang pregnant — again.

Smithsonian National Zoo officials say they performed two artificial inseminations Thursday on 18-year-old Mei Xiang.

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Officials say they were closely monitoring her for when to do the procedure. That’s because female giant pandas are only able to become pregnant for 24 to 72 hours each year. Officials say Mei Xiang’s estrogen levels peaked Wednesday, an indication she was able to become pregnant.

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Officials say Mei Xiang and the zoo’s 19-year-old male Tian Tian failed to breed naturally.

Mei Xiang has given birth to three surviving cubs: Tai Shan in 2005, Bao Bao in 2013 and Bei Bei in 2015. Bei Bei still lives at the zoo. Mei Xiang’s other offspring live in China.

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