At least 3 million people in the U.S. have celiac disease, an inherited autoimmune disorder affecting the digestive process of the small intestine. But the numbers may be much higher than that. The University of Chicago’s Celiac Disease Center says 97 percent of people with celiac disease are undiagnosed.

When a person with celiac disease consumes gluten — a protein found in wheat, rye and barley — the body’s immune system attacks the small intestine. The most common symptoms in adults are fatigue, joint pain, iron-deficiency anemia and gastrointestinal problems. Doctors can screen for the disease through blood tests and diagnose after an endoscopic biopsy that looks for damage on the small intestine.

Celiac disease is more prevalent in women. A recent study found pregnant women with undiagnosed celiac disease have greater risk of miscarriages and stillbirths. However, the risk minimized once the condition was diagnosed and treated.

For the study, researchers examined data from about 6,000 pregnant women with celiac disease and over 63,000 who did not have the diagnosis. The researchers found women who later received a diagnosis of celiac disease were 12 percent more likely to experience a miscarriage and 62 percent more likely to experience a stillbirth than women who did not have celiac.

The study results suggest that women experiencing fertility problems might want to be tested for celiac disease, especially if they have a relative with the condition.

What’s the recommended treatment for celiac disease? Experts advise that you follow a strictly gluten-free diet, which means avoiding all foods with wheat, barley and rye.