"The holidays just got jollier and that's a fact!" the cable network tweeted Monday, along with a link to a news report about the project.
Fields, who is also an executive producer on the film, told People.com she is responsible for the reunion.
"It's been amazing to work together again and have the ladies' input on their characters from their wardrobe to names, as well as provide fun inside jokes for fans," Fields said.
TVGuide.com said the movie will debut on Dec. 1 as part of the network's It's a Wonderful Lifetime programming banner.
The Facts of Life is a sitcom that initially aired 1979-88 and remains popular in reruns.