The HGTV "Fixer Upper" stars announced the news late Tuesday on Chip's Instagram account. He posted photo of him and Joanna petting his full belly with a caption that said, "Gains party of 7." This will be baby number five for the couple."If you're still confused.. WE ARE PREGNANT," Chip wrote. "Fixer Upper," which premiered in 2013, is in its fifth and final season. The couple announced in September that they will be ending the show to focus on their family and businesses. "Fixer Upper" follows the couple as the buy and remodel homes for their clients. Joanna serves the interior designer while Chip is the lead contractor. HGTV announced last year that Joanna would be getting her own spinoff show, "Fixer Upper: Behind the Design."Chip later took to Twitter to tell fans about the "romantic" Johnny Swim concert that led to baby number five. "You might recall a few months back," Gaines tweeted. "The ever amazing, ever romantic @JOHNNYSWIM was in Waco. And they put on a little too romantic of a concert.. anyways, one thing led to another, & we are officially pregnant. And I could not be more EXCITED! #5 #7ThePerfectNumber."Although the news of their growing brood may come as a surprise to their fans, Chip said in November that he'd love to have another child. "We had four babies right before the show started, and then we've had zero babies since the show started," he told Houston's KTRK. "For me, I'm really excited to go back and try to maybe … try to make some more babies."The newest Gaines baby will join siblings Drake, Ella, Duke and Emmie Kay. Joanna shared an ultrasound photo on Wednesday captioned,"Chip swears he can already tell it's a boy. Look at the little heartbeat!!"