These days when he isn’t rocking out with Fall Out Boy, Pete Wentz can often be found speaking to his unborn child or reading books about fatherhood.

“I talk to it all the time,” he told PEOPLE Saturday at the Ultimate Fighting Championship 86 afterparty in Las Vegas. “The Expectant Father tells you that the woman, when she speaks, the baby hears her all the time. And the father’s voice isn’t familiar unless you talk to it, so I talk to it all the time.”