WhenMaddie Brown Brushwent in for her routine ultrasound at 28 weeks pregnant, theSister Wivesstar knew something was wrong.

“It usually takes about 45 minutes, but the doctor just kept looking and looking,” Brown Brush, 23, tells PEOPLE in this week’s issue, on newsstands Friday. “I was stressing out the whole time.”

Finally, after more than two hours, the doctor told her to meet him in his office. “That’s when he told me, ‘I can’t find all 10 fingers,’ ” she recalls.

But when the reality star and her husbandCaleb Brushwelcomed daughterEvangalynn Kodion Aug. 20, the newborn was also missing a thumb and a toe, and one leg was missing a fibula (commonly known as the calf bone) and also had a bowed tibia (shinbone).

Hannah Hill photography

Maddie brown baby

Maddie Brown Brush’s daughter Evangalynn.Hannah Hill photography

Maddie brown baby

Evangalynn was diagnosed with fibular aplasia, tibial campomelia and oligosyndactyly (FATCO) syndrome, anextremely rare genetic disorderthat affects bone formation in utero. The cause is unknown. And because the disorder is so rare, it’s difficult to anticipate how Evangalynn’s future will look.

“How will she be at 70 years old? Will this come back and haunt her? There’s still a lot of unknowns, which is hard,” Brown Brush tells PEOPLE.

The family has to wait until Evangalynn turns 1 so that her body has more time to develop. At that time, they will consider options including surgery and amputation.

“There will be limitations, but not huge hindrances,” Brown Brush says, admitting she was initially hesitant tospeak out about her daughter‘s condition.

She adds, “It’s abnormal, and it catches people off guard, but I want her to grow up and feel proud about who she is. If I’m hiding this to protect her, is it really helpful?”

Brown Brush also wants to help others who may be dealing with the same issue. “So little is known about this, so I hope to bring awareness,” she says.

Sister Wivesreturns toTLCin early 2020.

For more from Maddie Brown Brush, pick up the latest issue ofPEOPLE, on newsstands Friday.

source: people.com