Jill Duggar Dillard and Derrick Dillard have lost their supposed-to-be fourth child.

Over the weekend, the "Counting the Cost" authors made the sad announcement via a joint post on Instagram and their blog regarding the loss of their first daughter, Isla Marie, from stillbirth.

Isla died in Jill's uterus on her fourth month of pregnancy.

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"It is with heavy hearts that we announce the stillbirth of our beautiful baby girl, Isla Marie Dillard. Jill was four months pregnant (due in August) when we found out that our baby died in utero," the couple wrote.

"From the moment we found out we were pregnant, we couldn't wait to meet our baby."

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Jill and Derick shared that Isla was dearly loved by her older brothers Israel, 9, Samuel, 6, and Frederick, 1.

"Isla was much loved from the start, and her three big brothers were so excited to introduce her to their world," they noted.

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Along with the sad announcement, the former reality stars expressed their appreciation for those praying for them amid the ordeal.

"We appreciate your prayers as we continue to grieve and heal from the loss of our little Isla Marie," they wrote in the post.

Their loved ones and followers quickly sent their condolences in the comments section and extended their sympathy to the couple.

"We love you all. We are continuing to pray. Isla Marie is so loved. Forever our first girl," commented Deena Dillard.

"Isla Marie is such a beautiful name and meaning. Praying continuously. God has a plan through all the heartbreak. You've been on my mind and in our prayers and will continue to be. We love you all so much," said Jill's cousin, Amy Duggar King.

"I'm so sorry for your loss. I can only imagine. Covering you guys in prayer," wrote one follower.

"May God be undeniably near to you all. I'm so sorry," said someone else.

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Jill, 32, is the fourth of the 19 children of Jim Bob and Michelle Duggar. She is known for her appearance in their TLC family reality series "19 Kids and Counting."

Her husband Derick, 35, who used to work as a tax accountant at Walmart, joined the reality show during their courtship.

However, the couple is no longer active on reality TV following the controversies involving Jill's Duggar family.

Last September, Jill and Derick released the book "Counting the Cost" alongside their co-author Craig Borlase. In the book, they shared the secrets behind the Duggars' traditional Christian family and how they "found healing through honesty."