A representative for the Wild Things actress revealed this week that she has adopted a newborn baby girl named Eloise Joni Richards from the US.
A source told US Weekly that the adoption process "has obviously been going on for quite some time" but that Richards wanted to keep the news from leaking publicly in order to maintain her family's privacy.
Richards is said to have decided to make the announcement about baby Eloise so that she could "leave the house" with her new daughter and older children Sam, 7, and Lola, 6, from her previous marriage to Charlie Sheen.
"The whole family is thrilled. Denise is a fabulous mother and the girls are great big sisters," the insider added.
Richards and Sheen, who divorced in 2006, were recently involved in a dispute after Sheen attempted to win full weekend custody of the girls but was denied.