Vomiting is less likely to be due to pregnancy if it begins after the 1st trimester of pregnancy. Vomiting is likely to be due to pregnancy if it lasts several days to weeks, abdominal pain is absent, and other apparent causes for vomiting are absent. If hyperemesis gravidarum is suspected, urine ketones are measured; if symptoms are particularly severe or persistent, serum electrolytes are measured. A normal intrauterine pregnancy should be confirmed to rule out hydatidiform mole. Other tests are done based on clinically suspected nonobstetric disorders.