'Big Bang Theory' star Johnny Galecki welcomes baby boy with girlfriend

The Big Bang Theory’s Johnny Galecki has welcomed a son with his 22-year-old girlfriend Alaina Meyer.

The actor, 44, announced their baby’s arrival by posting a black and white photo of the newborn’s hands, with his and Meyer’s, on Instagram.

Read more: Johnny Galecki to become a dad

He wrote: “With full and grateful hearts we welcome our beautiful son into this incredible world.

“Thank you for all of your love and support.”

Model and new mum Meyer shared the same message and image, but a colour version.

The baby is thought to be named Avery, as Meyer recently shared what seemed to be baby shower images with the name “Avery” in huge silver balloons.

She said at the time: “Avery’s comin into this world so loved, and with some hot aunties.”

Galecki and Meyer went public with their relationship last year and revealed in May that they were expecting a baby together.

The actor shared a picture of the couple on Instagram at the time and wrote: “We are absolutely over the moon to announce that we will soon be welcoming a little one into this crazy and wonderful world.

Read more: Johnny Galecki shares video of set being taken down

“We ask that you please respect our privacy during this celebratory time for us and our families.

“There truly is love out there for all.

“We hope ours is the ember of yours, as we feel yours is the ember of ours.”

They held a gender reveal party later that month, using blue paint to share that their baby was a boy.

“A day I’ll never forget,” the actor captioned a shot of the couple kissing.

Galecki is best known for playing Leonard Hofstadter in science sitcom The Big Bang Theory. He also starred as Darlene’s love interest David in hit comedy Roseanne.