50-80% of women experience heartburn due to gastro-oesophageal reflux during pregnancy. These symptoms become more prevalent after 20 weeks, but may occur in the first trimester. In late pregnancy, some women sleep in a sitting position.

Lower oesphageal sphincter tone is reduced in pregnancy. After 20 weeks, gastro-oesophageal reflux is also promoted by the presence of the gravid uterus.