Jill Duggar revealed that she was "very surprised" to find out last month that she and her husband Derick Dillard were expecting their first child, and shared photos of her growing baby bump on Instagram.

The "19 Kids and Counting" castmember reflected on the very moment that she knew she would be a mother in a recent interview. She also opened up about how her husband has been taking care of her.

"I was thinking that maybe we should take a pregnancy test", shared the 23 year-old Duggar, whose monthly cycle was unmistakably late. She took two pregnancy tests, and both were negative, so they were utterly amazed by the results of the third test.

"We were really surprised when we got that positive test," Duggar told US Weekly, "but of course we were really excited. I think we would have even been less surprised had it come back positive on one of the first tests."

When asked which family member persuaded her to take the third test, Duggar replied, "It was Jinger." Jill's 20-year-old sister was the first to know about her pregnancy.

"She was like, 'You know, mama has a bunch of pregnancy tests upstairs. You should take one of hers."

Jill thought the idea was funny, but took the test anyway just to prove her sisters wrong.

"That's where we took one of my Mom's pregnancy tests," Duggar reported, "and it came back positive."

Jill's husband, Derick, was also there when she took the test.

"He was thrilled," Duggar said.

At first there was some confusion when Jill's test returned positive. "One of the [previous] pregnancy tests had the little plus sign and the other one had the straight line. The one we had taken two days before was the one that was supposed to have the plus sign. The one I took at my mom's was just one line."

Laughing, Jill recounted how her husband saw the line on her third and final test and said emphatically: "No babe. Look! You're not pregnant.'"

However, the couple soon realised that the test result was positive.

"We were super excited," Duggar exclaimed. "We prayed together, and thanked God for this new little life. I was screaming and everything. [Derick] was like, 'Don't get too excited! You might stress out the baby or something.' He's so cute. He's so sweet."

In their excitement, the soon-to-be parents left the empty pregnancy test in Michelle and Jim Bob's bathroom.

"My mom texted me later inquiring about it," Jill said. "She was like, 'So I have a question! I found an empty pregnancy test in the trash can and your cup on the counter, so anything you want to share?"

Jill wanted tell her parents the news in person. "I was like, 'We'll wait and see,'" Duggar said. "It was funny. She had a suspicion there. She was thinking, 'something's up.'"

Derick and Jill found out they were pregnant on Aug. 20, just 60 days after their wedding. It was surprising to many "19 Kids and Counting" fans that Jill announced the expectancy news so early in the pregnancy, since a majority of miscarriages occur during the first trimester. However, it was important to the Christian couple to share their exciting news.

"Believing that life begins at conception and that every life is precious no matter how young, we would — even if there were to be a miscarriage — we would still want that child to be recognised," Duggar stated. "So it was something that we thought about and went forward with."

The couple has shared photos of Jill's growing baby bump on Instagram. The latest photo was taken when she was 11 weeks and two days pregnant.

"By the end of next week, all of our baby's body parts, from tooth buds to toenails, will be developing!" the expectant parents wrote in the caption, along with the hashtags "#firsttrimesterprogression #babydilly #19kidsandcounting."

The TLC reality show "19 Kids and Counting" airs on Tuesdays at 9 p.m. ET.