Changes in the respiratory system in pregnancy:

Changes in respiratory system during pregnancy: With the enlargement of the uterus, specially in the later months, there is elevation of the diaphragm by 4 cm. Total lung capacity is reduced by 5% due to this elevation. Breathing becomes diaphragmatic. Total pulmonary resistance is reduced due to progesterone effect. The subcostal angle increases from 68° to 103°, the transverse diameter of the chest expands by 2 cm and the chest circumference increases by 5–7 cm.  A state of hyperventilation occurs during pregnancy leading to increase in tidal volume and therefore respiratory minute volume by 40%.