The 35-year-old father-to-be shared on his Instagram a snap of rival Texas and Nebraska team football jerseys hung on a clothesline.
"Little guy is going to have a tough time deciding who to root for... But we'll love him not matter what school he chooses... Right @kiwiporter?," he captioned.
The due date is currently unknown.
Porter, known for his starring role as Jason Street on 'Friday Night Lights', has been married to Mayfield since April 2013 after a year of engagement.
They first met on the set of the NBC drama.