09/16/2013 at 11:00 AM EDT
shared a picture of her double-baby bump via Instagram on Saturday
The mom-to-be appeared pool-ready, sporting a black strapless bikini with white lace trim.
"Going swimming with the kiddos," she wrote in the caption. "This pool makes me feel so much lighter! This belly #twins #excited #blessed #nofilter."
The Don't Be Tardy
star, 35, announced in August
that she is expecting twins.
"I was completely shocked," she said at the time. "I had no idea. It was a natural conception, but twins do run in the family, so I guess I shouldn't have been surprised."
Zolciak is married to Kroy Biermann, a defensive end for the Atlanta Falcons. The couple have two children together, sons Kroy Jr.
, 2, and Kash Kade
, 13 months. Zolciak also has daughters Ariana, 9, and Brielle, 16.