Rousey earned her seventh consecutive first-round armbar victory, but just barely.
Carmouche put Rousey on the defensive after taking her back during a scramble and locking in a tight standing rear-naked choke.
Carmouche had Rousey wobbled, as she worked for a neck crank.
Rousey survived the sustained attack and then put Carmouche in a side headlock, while proceeding to deliver a flurry of punches.
Rousey also survived an up kick from Carmouche that landed clean to her left breast. The kick nearly ripped Rousey's top off, which would have caused an embarrassing wardrobe malfunction.
However, Rousey fought through it and locked Carmouche in a tight armbar.
Carmouche fought off the armbar attempt for the better part of a minute, but the powerful Rousey ultimately straightened out the limb and forced the tap-out with just a few ticks left in the opening frame.
"Is this real life right now? I'm not sure," Rousey said after her victory at UFC 157. "One thing I had to learn in MMA is be patient and take my time."
Luckily for MMA fans across the world, Rousey narrowly avoided a wardrobe malfunction at UFC 157.
No one can be quite sure if Carmouche threw the up kick on purpose, but it definitely got Rousey thinking. She took a few seconds to adjust her top to make sure her "twins" weren't showing, before getting her head back into the fight.
UFC 157 did not feature any other close calls with wardrobe malfunctions.