Chicago Zoological Society officials say three Brookfield Zoo bottlenose dolphins are pregnant.
Officials said Monday that 26-year-old Allie, 31-year-old Tapeko and 10-year-old Spree are due to give birth this summer and fall.
Allie has had two previous calves and Tapeko, three. But first-time mother Spree will require extra care as her pregnancy will have greater risks, as with other mammals.
Officials say zoological society field scientists, veterinarians and husbandry managers work together to improve the well-being of dolphins at Brookfield Zoo and in the wild.
Society associate veterinarian Jennifer Langam says prenatal care for the dolphins is similar to that for human moms, which includes ultrasound exams and blood tests.
Factors tracked during daily activities include weight gain, body temperature, diet and blubber thickness.