The former Coronation Street star took to Twitter to announce the happy news, writing, "Ryan & I are overjoyed to announce that we are expecting a baby! Feeling very blessed!"
The news comes just less than a month after Katherine and Ryan tied the knot in a secret wedding in Las Vegas, covered by HELLO! Magazine.
The star told her family that she had simply headed off on a well-earned holiday in August with her digital analyst manager boyfriend, but the lovebirds secretly married at the famous Little Church of the West.
"I love going to other people's weddings but I have never desired a big white wedding for myself and it has never been put on me as a pressure, an expectation," said Katherine, at the time. "The day was everything we hoped it would be — no fuss, low key, sunshine and just us!
"We'd been laughing and joking all day and then suddenly, everything seemed to stop and we tried to get the words "I do" out without becoming emotional wrecks. It was awesome. I'll never forget that moment for the rest of my life."
And explaining why she wanted to become a runaway bride and not tell her family of the nuptial, Katherine told HELLO!, "Selfishly, I just wanted Ryan to myself that day. So many people say you have to remember to grab hold of your bride or groom and spend time with them.
"I think if we had done a traditional wedding we would have been doing it for everyone else but this was about the two of us."