When Sarah Molitor learned she was pregnant last year, she said she assumed she would be a seven-time boy mom.

Molitor and her husband Tim, founders of Modern Farmhouse Family, a website and lifestyle brand, are already parents to six boys, ages 10, 8, 7, 5, 3 and 17 months.

"Especially knowing that this was our last child, I was just really thrilled and had settled into the fact of [having] seven boys. I almost felt an identity and a pride in that," Molitor told "Good Morning America." "Girl was not even in my mind a 1% chance."

Because this pregnancy would be her last, Molitor said she talked her husband into forgoing their usual routine of learning the baby's sex at the doctor's office themselves and then together telling their sons, as they had with each previous pregnancy.

For this pregnancy, Molitor and her family did a sex reveal using confetti so they would all be surprised and find out at the same time.

When pink confetti came pouring out of their confetti poppers, Molitor said she was in total shock.

A video of the moment shared on Instagram shows Molitor falling to her knees and crying in response.

"There was the realization that I'm not an all-boy anymore and that's not who I'm going to be," Molitor said of her reaction. "Then I was like, 'Oh my goodness, I'm having a girl.' That's the other side of the coin."

Even several weeks since learning her baby's sex, Molitor said she is still in shock.

"I know it to be true but I think there will still even be like 10% of me that at the birth will be like, 'Let's all check and confirm it's a girl,'" she said. "After 10 years of boys, it's hard to imagine holding a little girl in your arms and what that's going to be like."

Molitor said she is due in about nine weeks, on March 15. Her sisters are holding a baby shower for her later this month to supply her with the baby girl items she is lacking amid raising six boys.

She said her sons are very excited to meet their new sister.

"Every night they pray and say their names and then they say, 'And for our first baby sister who is coming soon,'" Molitor said.