Hyperemesis gravidarum refers to a condition where nausea and vomiting of pregnancy has progressed to a point where the patient has lost >5% of her initial body weight or has electrolyte abnormalities. The etiology and pathophysiology of hyperemesis are unknown but thought to be related to elevated levels of beta-human chorionic gonadotropin (beta-hCG) and size / mass of the placenta. It appears to be on the severe end of the spectrum of nausea / vomiting of pregnancy.

Most often, symptoms peak between 7-14 weeks of gestation and then usually resolve thereafter, although they could continue to be an issue throughout the pregnancy.

Risk factors include multiple gestation, personal or family history of hyperemesis, molar pregnancy, and having a female fetus.  

Diagnosis is one of exclusion of other potential causes of nausea / vomiting. Although there are no specific criteria, patients with hyperemesis usually have perceptible weight loss (approximately 5% of prepregnancy weight), ketonuria, and persistent nausea / vomiting. Some patients will have electrolyte imbalance as well.

Hyperemesis is the most common cause for hospitalization in the first trimester of pregnancy. 

Some studies have suggested that taking a multivitamin at the time of conception may help reduce the incidence of hyperemesis.

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