OITNB 's Lauren Lapkus Expecting 'Rainbow' Baby Girl with Husband Mike Castle: 'So Grateful'

Lauren Lapkus and Mike Castle

Lauren Lapkus is pregnant!

The 35-year-old actress, who has appeared on Orange Is the New Black and The Big Bang Theory, announced in an Instagram post on Tuesday that she's expecting a baby girl with husband Mike Castle.

"We are expecting a baby girl this summer," she wrote alongside a photo of herself cradling her baby bump while Castle, 32, held their beloved dog, Franny, in his arms. "I am over the moon. So grateful and happy."

Lapkus captioned the post with the hashtag "Rainbow Baby," a term used to describe a child born after a miscarriage, stillbirth, neonatal death or infant loss.

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Getty Images Lauren Lapkus

On his Instagram, Castle shared the baby news by posting a picture of himself gazing lovingly at Lapkus while wearing a sweater with the word "Dad" stitched across the chest.

"Can you even believe it?! Baby girl on the way this summer," the Brews Brothers star wrote in the caption. "#rainbowbaby."

The couple married in a courthouse ceremony on Oct. 5, 2018.

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Last year, Castle opened up to PEOPLE his relationship with Lapkus, sharing that he was "enamored" by the comedian even before meeting her.

"We could have met so many times," said the actor — who, like Lapkus, hails from Illinois. "Where I went to Piven Theater, that's blocks away from where Lauren grew up. It was very strange when Lauren and I eventually started dating, then I was like, 'I know this whole neighborhood so well and I've never met you.' "

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"She's just so fun and cool to be around," he added. "Before I ever start a job with anybody, I always do a slightly unnecessary amount of research on them. With Lauren, I listened to her podcast and I always thought she was funny and everything, but I remember when I heard the podcast I was just enamored. I couldn't believe how funny she is."