Background: Hyperemesis gravidarum is one of the many problems during pregnancy; its etiology has not been clearly understood. Inflammatory factors like helicobacter pylori infection has been considered as a risk factor in some studies. The aim of this work was to assess the relationship between infection with Helicobacter pylori (H.P) and the occurrence of Hyperemesis Gravidarum (HEG). Methods A case/control study, conducted at the department of Obstetrics and Gynecology, Zagazig university hospitals, during the period from May 2017 to February 2018. included 190 pregnant women who were in the first trimester of their pregnancies. 95 pregnant women with hyperemesis gravidarum and the other 95 pregnant women with the same gestational age but without hyperemesis gravidarum. In both groups, IgG for H.P was calculated and compared between the two groups. Results: There was statistically insignificant difference between the study groups regarding age or BMI parity, gestational age, gravidity and history of abortion. There were significant difference between both groups regarding Serum H. pylori IgG (p.value: 0.047) and stool H.pylori antigen (P.value