Respiratory disease in pregnancy

Breathlessness is a common pregnancy symptom, which nonetheless always merits careful history taking and consideration of the wide range of possible underlying causes. The physiological changes in respiration during pregnancy include an increase in minute ventilation, primarily due to increased tidal volume. The partial pressure of oxygen in the maternal blood is slightly higher than outside of pregnancy and that of carbon dioxide slightly lower. It is important to be alert to these expected parameters, and maintain a high index of suspicion where borderline partial pressures are noted in a pregnant woman. Respiratory problems during pregnancy may arise from the airways themselves (e.g. asthma), the pulmonary vasculature (e.g. thromboembolism), or from the mechanics of breathing (e.g. diaphragmatic splinting). In this review, a symptom-based approach to respiratory problems commonly encountered in obstetric practice is discussed.