Hospitalized newborns at an Illinois neonatal intensive care unit are celebrating their first-ever Halloweens in style.

Advocate Children's Hospital, located in Chicago's suburbs, posted pictures of their tiny patients dressed up in Halloween outfits on Wednesday. The infants were dolled up by their parents as part of a contest.

"Parents with babies in our neonatal intensive care units (NICUs) across Chicagoland are getting into the Halloween spirit!" the Facebook post read. 

"It's time to VOTE for your favorite in our annual Advocate Children's Hospital NICU Halloween Costume Bash," the hospital added, asking Facebook users to vote by liking their favorite pictures.

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Babies dressed up as ketchup and mustard bottles

Advocate Children's Hospital is holding a Halloween costume contest for their intensive care patients. (Advocate Children's Hospital via Facebook)

"We think they are ALL winners!" the post concluded.

Pictures show the babies yawning and sleeping in adorable costumes, ranging from superheroes to Disney characters to insects and animals. Many of the miniature costumes appeared hand-knit due to the youngsters' small statures.

Some of the sleeping infants were dressed as Wonder Woman and Batman, while others were dressed as caterpillars and scuba divers. Some of the captions described the children's medical conditions and the meaning behind their costumes.

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"Alaysia was born at just 23 weeks old. Since day one, she's been fighting a tough fight in the NICU," one of the captions read. "It’s fitting that Alaysia’s parents dressed her up as a little boxer/fighter as she truly is 'Mommy and Daddy’s little fighter'."

Sleeping infant dressed as a pumpkin

Advocate Children's Hospital asks Facebook users to vote in the contest by liking their favorite pictures. (Advocate Children's Hospital via Facebook)

The Illinois hospital, which has two locations in Oak Lawn and Park Ridge, will wrap up the costume contest at noon on October 28. The two babies with the most Facebook likes will win a prize.

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Neonatal intensive care units (NICUs) care for ill or premature newborns who require specialized care. The ailing infants often under four weeks old.