Background: Nausea and vomiting during pregnancy are the most common conditions affecting pregnancy, occurring in about 80% of all pregnancies and the condition always disappears on the 16th to 18th weeks of gestation. This may be mild and does not affect the general condition of the pregnant women (the condition is called emesis gravidarum), or it may be severe enough to affect the patient physically and psychologically, causing intractable vomiting, weight loss (0.5%), electrolyte imbalance, dehydration and impairment of liver and kidney functions. Helicobacter pylori (HP) is one of the most common bacterium affecting humans. It is gram-negative and helix-shaped microaerophilic bacterium transmitted by the oro-oral or feco-oral route. It is more prevalent in developing countries and affects young children. Acute infection manifests as acute gastritis and stomach pain, whereas chronic infection causes chronic gastritis and peptic ulcer, 2% of which may develop into stomach cancer. Aim: The aim of our study was to investigate the association between H pylori infection and hyperemesis gravidarum. Methods: Forty five pregnant women with hyperemesis gravidarum and 45 asymptomatic pregnant women in a prospective study were enrolled. Serum immunoglobulin G for Helicobacter pylori was assayed in the sera of the two groups. Results: Regarding maternal age, gestational age and socioeconomic status, there was no statistical difference between both groups. There was a marked statistical difference between both groups in terms of Helicobacter pylori seropositivity. Conclusions: There is a powerful correlation between H pylori and hyperemesis gravidarum.