<qa>  What is the most common cause of vomiting?Both groups were matched regarding the inclusion criteria which includes maternal age 18-40 years, gestational age 16 wks, and signs and symptoms of H.G for cases vomiting affecting the general condition, ketonuria, weight loss and excluding cases or controls with multiple gestation, hyadatiform disease or maternal disease causes vomiting such as ; pyelonephritis, gastroenteritis, cholecystitis or hepatitis. 