Answer:
Your eyes are an important part of your health. Most people rely on their eyes to see and make sense of the world around them. But some eye diseases can lead to vision loss, so it is important to identify and treat eye diseases as early as possible.
Birth defects can be caused wither by internal genetic factors or external factors like drugs, radiation, smoking,...
Dana, who is concerned about the possibility that her baby will have defects, may do the following tests: screening test, that will show if she might have child with birth defect and diagnostic test like amniocentesis (analyzing small amount of amniotic fluid from the area surrounding the baby) which is more than 90% correct.
A. A problem with the digestive system, possibly irritable bowel syndrome