United Kingdom, July 22 -- Derek Hough and Hayley Erbert are expecting their first child together.

The 40-year-old professional dancer and his 30-year-old wife - who tied the knot in Monterey County, California in 2023 - revealed in a joint Instagram video that Hayley is pregnant.

In the video, the pair share a hug before Hayley holds up some sonogram photos for the camera.

They captioned the post: "We can't believe the biggest thing to happen to us could be so small."

The couple met after she was cast as one of the dancers for his and sister Julianne Hough's Move Live Tour in 2014.

They started dating the following year and Derek proposed in 2022.

Dancing With The Stars judge Derek previously opened up about his and Hayley's plans ...