The 16-year-old has been a revelation this season and has reportedly attracted the attention of some of the world's biggest clubs.
Bellingham was an unused substitute for Saturday's draw with QPR but boss Pep Clotet feels he needs more time to recover from a heavy recent workload.
Clotet said on birminghammail.co.uk: "Jude has played a lot of games and I rested him on Saturday with a view to him playing this game on Wednesday.
"But young players manage the load different to full professionals, sometimes they take longer to recover and they get minor knocks and minor things.
"It was an intense game against Millwall (last Wednesday) and I want him to have a completely fresh, new start for Saturday.
"I know that will disappoint the fans, the fact he will not play against Premier League opposition. It is very simple, his team-mates need to win so we can play another Premier League team.
"He understands the situation, it's for his benefit. He has been coping with it very well, I want to make sure he can keep coping until the end of the league."
Leicester manager Brendan Rodgers had talked up Bellingham in his pre-match media, and the Foxes will certainly go into the clash as favourites to progress to the quarter-finals.
Birmingham reached the last eight most recently in 2011 and have not been further since 1974/75.
Blues will also be without influential winger Jeremie Bela, who suffered a hamstring injury against QPR.
Clotet estimates the Frenchman will be sidelined for around a month, which is better news than had been expected.
"Jeremie got a scan and it shows an injury on the hamstring area," Clotet said. "Initially it was very painful but it is milder than we expected. Luckily for us and happily for him.
"It is not going to be a very long one. He should be featuring for us. We have a lot of games to play."