Surprise!

Rosie O'Donnell announced on Twitter a short time ago that she and wife Michelle Rounds have a new baby girl.

With a photo of Rosie and Michelle holding the precious bundle, Rosie wrote: "we r thrilled to announce the arrival of r daughter Dakota - #withloveandthanks – AMEN."

Rosie's rep tells us the baby was born on Jan. 5 and weighed in at 5 pounds, 5 ounces. "Moms and baby are happy and healthy."

In January, Ro, 50, told Dr. Oz on his daytime talk show that Rounds, 41, was "trying to get pregnant."

After that interview, however, Rounds was diagnosed with desmoids tumors, a rare condition that requires multiple surgeries. And in August, Rosie suffered a heart attack.

The two, who got engaged in December 2011, married in June 2012.

Rosie already is mom to four older kids: Parker, 17, Chelsea, 15, Blake, 13, and Vivienne, 10. She split from wife Kelli Carpenter in 2007 after nearly a decade together. Dakota is the first child for Rounds.