Michael Phelps' Fetus Hits 1st Concert

Michael Phelps took his wife and his fetus out on the town on Tuesday -- treating the gang to a OneRepublic show!

Earlier that day, Nicole Phelps announced she was preggo with baby #2 -- but it wasn't until she hit the concert that she decided to show off her baby bump.

The Phelps' got to hang backstage with the band before the Phoenix show -- and tweeted about it, "These guys were amazing to see live the other night!! So talented!!!"

He's right. Counting Stars is a good song.