Can pneumonia can occur if a person does not use his lungs to breathe deeply very often?

No it can not occur that way but obviously it can lead to pneumonia slowly if you keep doing this unhealthy act.

Most kinds of pneumonia are contagious. Both viral and bacterial pneumonia can spread to others through inhalation of airborne droplets from a sneeze or cough.

Pneumonia occurs when you inhale bacteria into your lungs from food, drink, or saliva. This type is more likely to occur if you have a swallowing problem or if you become too sedate from the use of medications

a mother eats twice as much to support her growing fetus

limiting sugar intake in a mother with gestational diabetes, switching from diving to swimming.   depending on whether the patient is normal weight, over weight or gain will differ depending on that.