The newborn dolphin calf at Chicago's Brookfield Zoo died Thursday, just a week after she was born and only days after the zoo announced the birth of the dolphin calf and allowed media the opportunity to have a look.

The bottlenose dolphin calf was not nursing overnight Wednesday, zoo officials said, at which point the calf's health began to rapidly decline. Cardiopulmonary resuscitation (CPR) was administered to the calf in an attempt to save her, to no avail. The calf died at about 11:45 a.m. Thursday, zoo officials told the Chicago Tribune.

The calf was born last Thursday to a 26-year-old bottlenose named Allie. News of the birth was made public early this week and the media were invited to see the dolphin Wednesday.

The calf's death was unexpected; the zoo had released a promotional video of the unnamed calf and Allie swimming in their holding pool. Neither of the dolphins had been back on public display.

As Allie is an experienced mother, zoo officials initially said they were "cautiously optimistic" about the health and success of the calf in its first stage of life. However the first 30 days of a dolphin's life are extremely critical to development and a number of key milestones, such as nursing and "slipstreaming" must be met, regardless of the dolphin's position in captivity or in the wild.

"Allie's pregnancy progressed normally, and she has been provided proper nutrition and veterinary care throughout her pregnancy," Rita Stacey, curator of marine mammals for the Chicago Zoological Society, which manages the zoo, told the Chicago Tribune. "However, we remain cautiously optimistic as the first 30 days are extremely critical in the calf's life."

Zoo officials said dolphin calves often struggle to make it past the first 30 days of life.

"We see it both, unfortunately, in the wild and within a zoo setting," Dr. Michael Adkesson, vice president of clinical medicine for the Chicago Zoological Society, told the Chicago Tribune.

"It's a difficult situation with a young dolphin."

"As we were watching, we started seeing this weakness developing in the calf that would be associated with it just not being able to take in the up to the calf becoming nourishment or nurse the way that we would like to be seeing and that is probably been building for the immediate period leading weak," Adkesson told local Chicago CBS station WBBM.

A necropsy will be preformed to determine the cause of the calf's death.

The zoo has at least one other pregnant dolphin, which is expected to give birth this fall.