OBJECTIVES: The purpose of this study was to investigate the relationship between Helicobacter pylori infection and severe hyperemesis gravidarum (HG) by using Helicobacter pylori serological test. METHODS: Thirty eight patients with hyperemesis gravidarum and forty pregnant controls without hyperemesis gravidarum were included in this prospective study. Immunoglobulin (Ig) G concentrations were determined by enzyme-linked immunoadsorbent assay (ELISA) in patients with HG and controls. Chi square and Student t tests were used accordingly for statistical analysis. RESULTS: Positive serum H. pylori IgG antibody was detected in 47% (18 of 38) of the patients in the experimental group vs. 27% (11of 40) of the controls (P CONCLUSION: There is a significant association between Helicobacter pylori infection and hyperemesis gravidarum in our hyperemetic pregnant patients. Although H. pylori infection may be an important factor in exacerbating HG, it may not represent the sole cause of the disease.