A longitudinal study of respiratory changes in normal human pregnancy with cross-sectional data on subjects with pregnancy-induced hypertension

Structural and chemical changes induced by pregnancy alter the functioning of the respiratory system. The increase in the consumption of oxygen and the production of carbon dioxide during pregnancy do not upset the balance of acid and base in the blood. The respiratory changes during pregnancy have not been well studied. Respiratory changes were studied in 20 healthy pregnant women throughout pregnancy and after delivery. The resting tidal volume (the amount of air inhaled and exhaled during breathing), the minute ventilation (the amount of air expelled from the lungs per minute), oxygen consumption and carbon dioxide production all increased during pregnancy. The end-tidal carbon dioxide tension decreased progressively throughout pregnancy. The ratio of air expelled per minute to oxygen consumption was higher at the end of pregnancy than after delivery. There was no difference between respiratory changes occurring during a normal pregnancy and those during a pregnancy complicated by high blood pressure. (Consumer Summary produced by Reliance Medical Information, Inc.)