Katherine Heigl introduces son Joshua: 'We are beyond thrilled'

Jan. 25 (UPI) -- Mom-of-three Katherine Heigl is giving fans a first glimpse of her newborn son.

The 38-year-old actress shared a first photo Wednesday on Instagram of Joshua Bishop Kelley, Jr., her son with husband Josh Kelley, after welcoming the infant in December.

"@joshbkelley and I are beyond thrilled to finally share the arrival of our little man Joshua Bishop Kelley Jr born December 20th, weighing in at 7 pounds 15 ounces. We are all happy, healthy and beyond grateful!" Heigl wrote.

"Thank you to all of you for your wonderful words of support, love and all those beautiful well wishes! As always I am incredibly grateful to have such wonderful fans!" she added.

Heigl and Kelley married in 2007, and also share 8-year-old daughter Nancy and 4-year-old daughter Adalaide. The Grey's Anatomy alum appears on the Feb. 6 cover of People, and opened up about her son in the interview.

"It was a surprise! I knew I wanted to expand our family, I knew I wanted to have more children. I just didn't know how we were going to go about that," the actress, who adopted Nancy and Adalaide, told the magazine.

"This little boy is going to have all these girls fawning over him," she gushed. "We're at the point where we're really obsessed with him! With a newborn, you're forced to be still ... and you have this beautiful reason to do that."

"I'd get pregnant again, and I'm still very inspired by adoption. I also have been thinking a lot about fostering. It's all up in the air," the star shared. "And I'm okay with that!"

Heigl is known for playing Izzie Stevens on Grey's Anatomy, and has since portrayed Charlie Tucker on State of Affairs. She will next star on the CBS series Doubt with Steven Pasquale and Laverne Cox.