The couple brought six-year-old twins Jay and Rocco to the prenatal scan, he has revealed.
But Nicky and Georgina don't want to know whether their twins will be celebrating the arrival of a little brother or sister and have decided not to find out the gender of the baby before the birth.
“We were wondering how we’d manage to find out the baby’s gender without the two boys hearing,” Nicky said, “but in the end we said we’d keep it a surprise for all of us.”
Speaking on Today FM this morning, Nicky joked they will just have to paint the new baby’s bedroom white or cream.
The couple are due their third child in late October and brought six-year-old twin sons Rocco and Jay to Georgina’s last scan.
The former Westlife star has just returned from a summer break in Portugal with wife Georgina and is ready for his debut on RTÉ’s new reality TV show, The Hit, tonight.
The show is set to kick off with contestants The Stunning and Julie Feeney.
“There are five weeks of rounds before the big final,” Nicky said.
“It’s a magnificent show where unknown Irish songwriters will be pitching their songs to artists. The race will be on for the artists to choose the song they think could become a hit."
Both songs chosen by the contestants will be released on iTunes straight after the show and their progress in the charts will be tracked before next week's round.
Whichever artist’s song climbs higher in the Irish charts will make it through to the grand finale.
“It’s set in the O2 and the place just looks amazing," Nicky said.
"Everybody’s friends and family are there and the atmosphere is just electric.”
The Hit, presented by Nicky Byrne and Aidan Power, kicks off tonight, Friday July 26, on RTÉ One at 9:35pm.