Asthma in pregnancy.

The main pregnancy-induced changes in respiratory physiology are increased minute-ventilation, due primarily to an increase in tidal volume; a 20 per cent decrease in the functional residual volume; and a decrease in the arterial pCO2 resulting from increased alveolar ventilation. The management of acute asthma is changed very little by pregnancy. Beta-adrenergic agonists, theophylline, and glucocorticoids are all as safe as they are in the nonpregnant state; they are not teratogenic. Iodides are contraindicated in pregnancy. Ephedrine and combination products containing theophylline are best avoided during pregnancy, not because they are dangerous but because better preparations are available.