The 30-year-old presenter admits he feels uncomfortable in hospitals and is concerned about how he will react when he is supposed to be supporting his spouse when she has their twins in around two months time.
He tweeted: "I am probably going to faint in the delivery room! I need to man up!
"Or maybe I should say WOMAN UP since they are the ones that have to be the strongest in the whole ordeal! I am in awe of my wife!
"People are trying to give me advice for when that day comes. I`m trying to prepare but I get queasy in hospitals LOL. (sic)"
Nick and Mariah, 41, recently celebrated the impending arrival of their son and daughter with a baby shower at the Conservatory Grill at the Montage hotel, where they were joined by friends including talk show host Piers Morgan, `American Idol` judge Randy Jackson and director Brett Ratner.
Mariah said afterwards: "I`d never been to a baby shower. This was my first one - it was so festive!
"Nick and I were so grateful to everyone who came to celebrate with us. It was a night I will never forget."