The pair, who are already parents to Luna, 4 and 2-year-old Miles, made the announcement in the video for John's new single, "Wild," last month.
In one very specific shot in the video, John and Chrissy could be seen stroking her growing bump.
And Chrissy went on to confirm the news on Twitter, revealing that after experiencing fertility issues and conceiving her first two children using IVF, this third pregnancy had come as quite a surprise.
However, it seems that all is well and Chrissy's pregnancy is progressing perfectly.
Well, John has now opened up about the pregnancy for the first time, revealing that the idea to announce it in the video for "Wild" was a last minute decision from Chrissy since she was still in the very early stages.
"She was kind of hedging her bets," John told People, "Because we were early in our pregnancy. We hadn't taken all the tests to make sure everything is OK, and she said, 'Let's just shoot it,' and by the time the video would be edited, we could decide whether or not to use that scene."
"Then all the tests came back great and everything was healthy and good, so we knew it wouldn't be too early to tell people we were pregnant by that point," he continued.
"By the time the edit was done, we were comfortable saying to the world that we were pregnant," he added.
John went on to reiterate Chrissy's earlier comments that the news came as a total surprise to the couple.
"We weren't actively trying," he said, "Other than the actual act of doing what one does to procreate, we weren't trying to have a baby at that time."
"We just didn't think we could have a baby the old-fashioned way, honestly," he said.
"I believed that there would be a quarantine baby boom, with all these couples spending more time together," he added. "But I figured it wouldn't happen to us because we've had fertility struggles. And now it's happened to us, too!"