The Second Trimester: Shortness of Breath
As your baby gets bigger inside your body, there will be increased pressure on all of your organs, including your lungs. You might begin to notice that you are short of breath or might not be able to catch your breath. Try taking deep, long breaths and try to maintain good posture so your lungs have room to expand. You might be able to breathe more freely at night by using an extra pillow or by sleeping on your side.
If you sleep on your left side, you will relieve pressure on major blood vessels that supply oxygen and nutrients to the fetus. If you have high blood pressure, it is even more important to be on your left side when you are lying down.