Katherine Heigl's surprise Christmas baby

Josh Kelley and Katherine Heigl welcome another special member to their family. Photo / Getty

Katherine Heigl gave birth to her third child last month.

The 38-year-old actress and her husband Josh Kelley welcomed a little boy named Joshua Bishop Kelley, Jr., into the world on December 20, according to People.

The couple already have two daughters Adalaide, four, and Naleigh, eight, together but this was the first time Katherine has given birth to a baby as the girls were adopted.

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Happy New Years Eve from the Kelley girls! Here's to a spectacular, joyful abundant 2017 for all! 🎉👏😘

A post shared by Katherine Heigl (@katherineheigl) on Dec 31, 2016 at 6:33pm PST

The 'Grey's Anatomy' star - who lives in Utah with her family - announced her pregnancy in June and admitted she couldn't wait for her family of four to grow into a five.

She said at the time: "The Kelley clan is thrilled to announce that we are expecting a third addition to our family. Naleigh and Adalaide could not be more excited to welcome their new sibling into the fold, and Josh and I are overflowing with joy and gratitude. This is an incredibly exciting time for us filled with hope, anticipation and hormones. Well, only I'm filled with hormones, but everyone in the family gets to enjoy them. We couldn't be more excited to be able to finally share this news with our fans, and are looking forward to continuing to share the journey with you all."

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Daddy/daughter work session. How @joshbkelley comes up with new material! I think they're on to something! #daddysgirls #thoseheavenlydays #badlandsranch

A post shared by Katherine Heigl (@katherineheigl) on Jan 3, 2017 at 6:41pm PST

The blonde beauty kept her fans updated with her pregnancy throughout the second and third trimester and shared that the only way she could stay fit was through yoga.

She said: "It's hard enough for me to get motivated to workout when I'm not pregnant but now that I am it's 10 times harder. I'm not up for weight training, cardio workouts or any of those new and fashionable exercise classes. What I am up for is yoga!"

But the talented star was a little cautious throughout her pregnancy as her doctor had previously reminded her that carrying a baby at a mature age can be risky for some.

Katherine Heigl before giving birth. Photo / Getty

She explained: "We were considering adoption again, fostering, or pregnancy if possible.

Seeing as I have never been pregnant and as my OB/GYN reminded me last year, I'm of advanced maternal age, I wasn't sure pregnancy was even in the cards for us. Turns out it was very much in the cards!"

Josh Kelley and wife Katherine Heigl are seen on a walk September 24, 2016 in Los Angeles, California. Photo / Getty