Fiona the Hippo

The premature hippo that almost didn't make it — but did, and captured the hearts of millions in the process — turns 6 years old Tuesday.

“Bibi and the baby are doing great together. They are inseparable, which is why it took almost five days to be sure about the sex,” said Cincinnati Zoo’s director of animal care, Christina Gorsuch.

The wait is over, Bibi has given birth to a second hippo calf, making Fiona a big sister.

The Cincinnati Zoo confirms speculation that Bibi is expecting. Her expected due date is around mid-August.

The Cincinnati Zoo says the baby hippo that defied the odds has finally hit the 1,000-pound mark. Senior keeper Jenna Wingate says 1,000 pounds doesn't…