Most people are well aware of the myriad changes a body goes through during pregnancy - even the lungs go through interesting and intelligent alterations to adapt to the developing baby. In fact, one of the most confounding aspects of taking care of a pregnant patient is that it is normal for her to be short of breath. This makes it difficult to discern a 'normal' breathlessness from a problem that requires medication.
The Pregnant Body
A woman's body adjusts gradually as the pregnancy develops. Since a pregnant patient is carrying more weight, the lungs need to accommodate to the additional work of breathing caused by the weight gain. A pregnant woman breathes a little faster than normal, which is perfectly healthy. The body is raising what is called the minute ventilation (the amount of breathing you do in a minute).
As the belly grows, it alters the shape of the bottom part of the chest. The chest is separated from the belly by a swathe of muscle called the diaphragm, which is a vital muscle that helps you to breathe. As the belly gains in girth, it pushes upwards against the diaphragm, preventing deep breaths and consequently increasing the respiratory rate. To make the chest a little bigger, the ribs splay outwards like bucket handles, letting the patient breathe a little deeper.
