But on Monday, the 35-year-old mother of four said she was actually expecting twins.
"I'm having twins and I couldn't be more excited. I was completely shocked. 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," she told E! News on Monday.
"I can't believe I am going to be a mom to six children. It's going to be very busy but it's a dream come true," she added.
The added pressure of twins is reportedly making the experienced mom a little more nervous than usual.
"Kim is having a lot of anxiety about her pregnancy, she's completely changed her ways," a source told Us Weekly. "She's reached out to some nutritionists and other specialists about staying healthy as of recent."
Zolciak showed off her growing baby bump in an Instagram photo last month.