Chrissy Teigen wasn't sure if her unborn baby was ''okay'' before filming her husband John Legend's 'Wild' music video.

The 34-year-old model and her husband used the music video to announce they are expecting their third child together, but John - who already has Luna, four, and Miles, two, with his wife - has now revealed they filmed the scenes before they were ready to tell the world the good news.

John, 41, says Chrissy ''hadn't taken all the tests'' to make sure her baby was healthy when the footage was filmed, but decided to go ahead with the production anyway, with the plan to leave out the pregnancy reveal if something had gone wrong.

He said: ''She was kind of hedging her bets, because we were early in our pregnancy. We hadn't taken all the tests to make sure everything is okay, 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 that we were pregnant by that point. So by the time the edit was done, we were comfortable saying to the world that we were pregnant.

''But at the moment, it was more like, 'Let's shoot it, and if we're able to use it, we can. And if we can't, we can't.' ''

The 'All of Me' hitmaker also revealed the baby news came as a surprise for the pair, because they weren't ''actively trying'' to conceive.

He added: ''We weren't actively trying - 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 were in quarantine, and spending a lot more time together. And here we are.''

John and Chrissy have been open about their fertility struggles in the past, and after welcoming both their current children via IVF, John was shocked when Chrissy managed to get pregnant ''the old-fashioned way''.

Speaking to People magazine's senior editor Janine Rubenstein during a conversation for Meredith's ':BLACKPRINT' series, he said: ''We just didn't think we could have a baby the old-fashioned way, honestly. I believed that there would be a quarantine baby boom, with all these couples spending more time together. And I would joke about it, but I figured it wouldn't happen to us because we've had fertility struggles. And now it happened to us, too.''