"I really appreciate all the Congrats from each and every 1 of u today! We are so excited and so blessed! Thanks again!" Zolciak, 33, Tweeted Tuesday.
In another post, Zolciak hinted that she'll be embarking on a new fashion endeavor during her pregnancy.
"Meeting today about the baby clothing line!!! So excited!!!!!! #bigthingshappening," she wrote.
The baby will be the second child in as many years for Zolciak and her husband, NFL player Kroy Biermann, who wed last November. Their son, Kroy Jagger, Jr., was born last May. Zolciak also has two daughters from previous relationships.
On Tuesday, in response to one Twitter user who asked, "What does it feel like 2 have all ur dreams come true?," Zolciak responded: "Amazing! I'm so grateful!"