How could lung disease affect a pregnant woman?

Harder to breathe. During the normal course of pregnancy it gets harder and harder to perform usual activities. Any condition that affects the lungs will make things worse. In most cases, matters can be medically managed. In extreme cases, pregnancy can become a health threat to the mother.
It does. Lung disease becomes important in pregnancy as the enlarging uterus puts pressure on the diaphragm & limits the expansion of lungs in later stages of pregnancy. Also pregnancy & delivery are states of increased overall metabolism & requires adequate lung reserve to withstand these stresses. The type & severity of underlying lung disease can determine this risk. Please consult a lung specialist.