Level 1: Causes and symptoms of pregnant women coughing with phlegm. Causes of pregnant women coughing with phlegm may include respiratory infections such as colds, flu, bronchitis, or asthma or sinusitis caused by allergies. Symptoms include throat discomfort, cough, chest tightness, shortness of breath, etc. Level 2: How to treat pregnant women with cough and phlegm during pregnancy. When treating respiratory infections during pregnancy, you should avoid using products containing antipyretic ingredients.