Up to 85% of women suffer nausea and vomiting during the first half of pregnancy. Between 30% and 35% of these suffer symptoms that are severe. Hyperemesis gravidarum refers to the most severe form of nausea and vomiting and affects 0.3–1.0% of pregnant women.

There are medicinal and non-medicinal treatments for nausea and vomiting. Changes in diet or lifestyle are often the first treatments women might try. Similarly, women may buy vitamins B6 and B12, or ginger supplements. Other therapies may also be purchased or recommended by a health-care practitioner (e.g. acupressure/acupuncture). Some interventions need to be prescribed such as antiemetic drugs. A small number of women with severe symptoms may receive intravenous fluids, corticosteroids and assisted feeding.

Our results suggest that ginger preparations, vitamin B6, antihistamines and metoclopramide were better than placebo for mild disease. Effectiveness of treatments in more severe disease is unclear and evidence limited. Antihistamines, metoclopramide and ondansetron appear to be effective for some women, but there is no strong evidence to say which is better than the other. The overall quality of the evidence was low or very low for all treatment comparisons due to clinical differences between studies, poor and incomplete reporting of outcomes and concerns regarding risk of bias. Of note, however, was the finding that symptoms tended to improve after a few days (even with placebo). Therefore, we inferred that if symptoms have not improved, or not improved sufficiently after a short time, a change of treatment could be considered.