Tique is expected to give birth to her calf in mid-May.
Tique returned to the Shedd Aquarium in the fall of 2010.
Ken Ramirez, executive vice president of Animal Collections and Training at the Shedd, says there are fewer than 20 of the dolphins in North American facilities.
Tique is 26 years old and weighs about 200 pounds.
Dolphin pregnancies last approximately 12 months.
The Associated Press contributed to this report.
