BACKGROUND & AIMS:Heartburn and gastroesophageal reflux disease (GERD) during pregnancy are accepted as an innocent condition. The effect of heartburn during pregnancy on the initiation or progress of GERD is not known. We aimed to determine the predisposition effect of heartburn during pregnancy for presenting with GERD in the future. METHODS:A validated reflux questionnaire was applied to 1180 randomly selected women aged between 18-49 years who had given birth to at least one delivery. Frequent symptoms were defined as a major symptom (heartburn and/or regurgitation) occurring at least once a week or more. Occasional symptoms were defined as an episode of one of the major symptoms occurring less than once a week within the past 12 months. RESULTS:The mean live delivery rate was 2 +/- 1 (range, 1-10). The prevalence of GERD was 7.4%. Whereas the prevalence of GERD for women with a history of just 1 delivery was 1.5%, more than 2 deliveries were accompanied with risk of 15.1% (P < .001). In the group with no heartburn during pregnancy only 5.5% had GERD (P < .00001). If there was heartburn during any of the pregnancies, the risk was 17.7%; and more than 2 pregnancies with a history of heartburn accompanied 36.1% risk of having GERD. Logistic regression analysis showed that the risk is independent from obesity and age. CONCLUSIONS:The risk of GERD is increased by the presence of heartburn during pregnancy. This association is independent of obesity and age. Heartburn during pregnancy might not be accepted as an innocent and temporary condition.