The new baby would be Zolciak and the Atlanta Falcons defensive end's third baby together, as the couple just welcomed their second son Kash in August 2012 and had their first son "KJ" Kroy Jagger in June 2011. Zolciak also has two daughters 16-year-old Brielle and 11-year-old Ariana from a previous relationship.
"Kim and Kroy are so excited to be pregnant again," a source close to the couple told Life & Style. "She's been trying to keep it quiet -- she didn't realize she's showing as much as she is."
Added the source, "They didn't plan it, but they're thrilled."
While the new alleged pregnancy might have come as a surprise, according to Us Weekly, continuing to expand their family was never out of the question for the reality TV couple.
"Kim loves being pregnant. She really wants a little girl," an insider told Us, adding that Biermann is also hoping to have a daughter.
"Brielle and Ariana are older now, and Kroy wants a girl of his own."
Zolciak and Biermann tied the knot in November 2011 after getting engaged the prior month.