Whitney broke the news to fans Thursday ... saying her mom died Wednesday "just as the credits rolled on her favorite movie." She says the time she passed -- 10:32 PM -- was also the exact time Whitney was born back in 1984.

Whitney says her mom suffered from cerebral amyloid angiopathy ... an unfortunately untreatable condition that can cause brain bleeding, strokes and dementia. She says Babs had been having strokes since 2017.

She goes on to share her love for her mom, and her pain about the tragic loss -- she ends the post directed at the fans, "We are unbelievably thankful that we've been able to share her with you and it is our hope that her memory will continue to be a source of comfort and happiness for the rest of your lives ... I love you, mommy."

Fans of the show remember Babs in all 10 seasons of the TLC show ... as the series progressed, a portion of the show began focusing on her health struggles with her condition.

The 10th season saw Babs' road to recovery, and release from the hospital after suffering one of her strokes. TLC has yet to announce whether the hit series will return for the 11th season.

Babs is survived by Whitney, as well as her son, Hunter, and her husband, Glenn.

She was 76.