The Oklahoma native -- who memorably gave birth to son Gannon in September 2011 during the fourth season of 16 and Pregnant and then welcomed daughter Jaxie Taylor in February 2014 -- will welcome her brand-new addition with husband Josh McKee in early September, according to Us Weekly.
Even though the former cheerleader has not dropped any social media hints about her bundle of joy on the way -- or shared any selfies of her burgeoning belly -- a source told the magazine that the young mother is 20 weeks along. Let's see that bump, mama!
Be sure to wish Mackenzie, Josh and the rest of the clan your congratulatory messages in the comments. And for a blast from the past, check out one of Gannon's earliest -- and cutest -- moments from his 16 and P episode!