Lower esophageal sphincter pressure in women using sequential oral contraceptives.

Lower esophageal sphincter pressure, basal gastric pH, and fasting plasma gastrin were measured sequentially in female volunteers who were using oral contraceptives. No difference in basal gastric pH or fasting plasma gastrin was observed during any of the three selected periods studied. Lower esophageal sphincter pressure was the same during menses (20.8 +/- 1.7) when the volunteers took no medication during the phase of the cycle when the volunteers were ingesting ethinylestradiol (18.3 +/- 1.7). Lower esophageal sphincter pressure decreased significantly (P less than 0.01) to 9.4 +/- 1.2 during the phase of the cycle when the volunteer took the progestation agent, dimethisterone, as well as ethinylestradiol. It is therefore proposed that the progessive rise in plasma progesterone alone or in combination with estrogens that occurs during the course of pregnancy might be responsible for the increased incidence of symptomatic heartburn in pregnant women.