Cincinnati Zoo's Fiona is going to be a big sister!

Cincinnati's favorite hippo is going to be a big sister!

Fiona, who was born six weeks premature in January 2017, will be a sibling when her mom, Bibi, gives birth later this year, the zoo said.

The Zoo tweeted a photo of an ultrasound on National Sibling Day, but didn't provide any context.

“The hippo team is excited and also nervous,” said Eric Byrd, manager of Cincinnati Zoo’s Africa team. “As most people know, Bibi’s first baby, Fiona, was born six weeks premature and wouldn’t have survived without the intervention of her human caregivers. We are hoping for a full-term pregnancy and will be doing everything we can to support Bibi.”

The daddy hippo, 18-year-old Tucker, was "enamored with 23-year-old Bibi right away" when he was introduced to the hippo habitat last September, the zoo said in a press release.

“We weren’t planning to welcome a baby this soon, but nature found a way and ignored our calendar,” said Cincinnati Zoo’s director of animal care, Christina Gorsuch. “Most forms of contraception, in hippos or humans, (are) not 100% reliable. The dose that was previously effective for Bibi did not prevent pregnancy this time.”

The zoo did not provide an estimated birthday, but said they will share updates on Bibi and baby preps in the months leading up to the birth.

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