Women in normal labour may sometimes go on to have general anaesthesia if labour becomes abnormal, for example if a caesarean section is required. General anaesthesia carries a very small risk of regurgitation and inhalation of stomach contents into the lungs. This can cause inflammation, particularly if the fluid is acidic, and can lead to severe morbidity and very occasionally mortality. Labour hormones increase the risk of gastric aspiration or Mendelsohn's syndrome, though the exact incidence is unknown. The routine administration of acid prophylaxis drugs to all women in normal labour is commonly practiced worldwide, to reduce gastric aspiration by reducing the volume and acidity of stomach contents.