Hyperemesis gravidarum is excessive nausea and vomiting of pregnancy (that is, morning sickness) that goes beyond the normal gastrointestinal disturbance experienced by many women. Its exact cause is unknown. The condition is diagnosed when nausea and vomiting trigger one or more of the following symptoms:

• Weight loss

• Ketosis/ketonuria

• Dehydration

• Electrolyte imbalance

Other conditions that can cause similar symptoms — including hyperthyroidism, pancreatitis, gall bladder or liver disease, gastritis, appendicitis, and ectopic pregnancy — should be ruled out before diagnosing hyperemesis gravidarum. Treatment typically involves intravenous therapy to rehydrate and encourage weight gain (parenteral nutrition).

Hospitalization may be required, and medications may also be prescribed. Infants of mothers who experience this condition are more likely to have lower birth weights and to be small for gestational age.

Fortunately, hyperemesis gravidarum is relatively uncommon, occurring in less than 1 percent of pregnancies.