By Breaking Celebrity News Staff

Four isn't enough for Rosie O'Donnell.  She and her fiancée Michelle Rounds are hoping to add to her brood with another baby.

"She's trying to get pregnant," Rosie told guest Dr. Mehmet Oz on an episode of her talk show Friday.

O'Donnell and Rounds have had a whirlwind romance.  They met at a Starbucks, and became engaged only a few months later, in early December.

"Michelle is seeing a fertility doctor," a source told Us magazine. "She is really excited and they cannot wait to add to their family. Rosie goes to all of her doctors' appointments with her and is really supportive."