On The View Thursday, he said he won't sleep with his wife because she keeps trying to get pregnant.
"She [says] she is not going to tell me she is going to go off her birth control," Pratt, 26, said on The View Thursday.
Not sleeping with her is "the only thing I can think of in my defense," he said.
Montag, 23, insisted she isn't intentionally forgetting to tell him.
"I would tell him the truth, but sometimes mistakes happen," she said. "Sometimes you accidentally miss one. It happens."
Montag said she wants kids "sooner than later," adding, "My mom was a young mom."
But Pratt is so adamant about not wanting them, "He says he wants surgery," Heidi said.
She said he "joked" about not wanting kids before they got married, but she never took him seriously.
"I thought we would get married and then go to that hurdle -- marriage and then kids at the same time," she said.
She said "it's only four months. We're supposed to be in the honeymoon phase.
More on Wonderwall:
More on Usmagazine.com: