It is normal for pregnant women to experience shortness of breath during the 16th week of pregnancy. This occurs due to various factors such as hormonal changes, increased blood volume, and the growing uterus putting pressure on the diaphragm. As a result, your lung capacity may be reduced, making you feel out of breath more easily. To alleviate this symptom, try practicing deep breathing exercises, maintaining good posture, and taking frequent breaks when needed. If you are concerned about your symptoms or they worsen over time, consult with your healthcare provider for further evaluation and guidance.