In the first trimester of pregnancy, basal lower oesophageal sphincter (LES) pressure may not change, but is less responsive to physiological stimuli (i.e. pentagastrin, edrophonium chloride, methacholine or a protein meal) that usually increase LES pressure.[1,4] In the later two trimesters, LES pressure gradually falls approximately 33-50% of basal values reaching a nadir at 36 weeks of gestation and rebounds to pre-pregnancy values 1-4 weeks postpartum. Animal and human studies find that the increased circulating levels of progesterone during pregnancy mediate the LES relaxation, but oestrogen is a necessary primer. The secondary role of increased abdominal pressure because of the enlarging gravid uterus is more controversial. All studies agree intra-abdominal pressure increases with pregnancy. It is unknown whether the normal compensatory response of the LES to increase to these changes is impaired during pregnancy. Others have suggested that abnormal gastric emptying or delayed small bowel transit might contribute to heartburn in pregnancy.
Aliment Pharmacol Ther. 2005;22(9):749-757. © 2005 Blackwell Publishing
Cite this: Review Article: The Management of Heartburn in Pregnancy - Medscape - Nov 01, 2005.