Evidence refuting a role for increased abdominal pressure in the pathogenesis of the heartburn associated with pregnancy.

As a model of pseudopregnancy, the lower esophageal sphincter pressure and plasma gastrin and basal gastric pH levels were determined before and after diuresis in 10 men with tense ascites due to cirrhosis of the liver. Prior to diuresis, when abdominal pressure was increased, sphincter pressure was increased. After diuresis, when ascites was no longer a clinical problem, sphincter pressure was normal. None of the men had heartburn or demonstrable acid reflux either before or after diuresis. In addition, no differences in basal fasting levels of gastrin or gastric pH were noticed before and after diuresis. This study refutes a role for increased abdominal pressure due to an enlarging uterus in the pathogenesis of the heartburn of pregnancy. Moreover, it is consistent with those studies which suggest that increasing progesterone levels seen during pregnancy induce a loss of basal lower esophageal sphincter pressure and thereby allow the occurrence of acid reflux which produces symptomatic heartburn.