Jen Affleck's family's getting a little bigger, and her belly is too ... she's pregnant with her fourth child!

The 'Secret Lives of Mormon Wives' star announced the news in a series of photos she shared to social media Thursday ... and the snaps have a vintage, classic look to them.

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Jen's wearing a flowing white dress in the shots and holding her baby bump ... absolutely glowing as she flashes a flawless grin to the camera.

She captioned her post, "Chapter Four. 🤍"

Jen and her husband Zac have been busy building their family over the last few years ... they also share a daughter, Nora, who turns 5 in the fall and a son Lucas who will turn 3 next month. In July 2025, they announced the birth of their youngest, Penelope.

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Fans have been speculating online in recent months that the two were going through marital issues ... especially after Jen posted a tearful TikTok in which she talked about her "next chapter" and wasn't wearing a wedding ring.

Regardless, Jen's life will soon be changing once again ... and she looks over the moon about it!