The "19 Kids & Counting" stars are already parents to Mackynzie, 5, Michael, 4, and Marcus, 2.
Back in March, Anna Duggar revealed to People magazine that they'd be having another girl.
"I feel so good right now. And we can feel the baby move now, which is fun for the kids to get to feel their little sister moving around," she said. "Some people think I'm not happy unless I'm pregnant."
It's been an emotional year for the Duggars. Their show was pulled from the TLC schedule after Josh Duggar responded to allegations of molestation that happened years ago starting when he was 14 years old. He's 27 now.
"Twelve years ago, as a young teenager, I acted inexcusably for which I am extremely sorry and deeply regret. I hurt others, including my family and close friends. ... I sought forgiveness from those I had wronged," he said in a statement on Facebook.