Treatment of nausea and vomiting in pregnancy. When should it be treated and what can be safely taken?

Nausea and vomiting are both common in early pregnancy. Most cases are mild and do not require treatment. However, persistent vomiting and severe nausea can progress to hyperemesis if the woman is unable to maintain adequate hydration, and fluid and electrolyte as well as nutritional status are jeopardised. Hyperemesis gravidarum is a diagnosis of exclusion, characterised by prolonged and severe nausea and vomiting, dehydration, ketosis and bodyweight loss. Investigation may show hyponatraemia, hypokalaemia, a low serum urea level, metabolic hypochloraemic alkalosis and ketonuria. The haematocrit is raised and the specific gravity of the urine is increased. There may be associated liver function test abnormalities and abnormal thyroid function tests, with biochemical thyrotoxicosis with raised free thyroxine levels and/or suppressed thyroid-stimulating hormone levels. The pathophysiology of hyperemesis is poorly understood. Various hormonal, mechanical and psychological factors have been implicated. Studies have demonstrated a direct relationship between the severity of hyperemesis, the degree of biochemical hyperthyroidism and the levels of human chorionic gonadotrophin (hCG). Management of hyperemesis should include hospitalisation, intravenous fluid and electrolyte replacement, thiamine (vitamin B1) supplementation, use of conventional antiemetics and psychological support. Most patients improve spontaneously with the help of the above measures without long term sequelae. Conventionally, antiemetics are not usually prescribed, especially before 12 weeks gestation, except for women with hyperemesis. This reluctance relates to fears which are often unfounded concerning the teratogenic effects of antiemetics. Severe hyperemesis, refractory to conventional management with intravenous fluids and antiemetics is a rare, miserable and disabling condition, associated with multiple hospital admissions, time away from work and the family, and psychological morbidity. If inadequately or inappropriately treated, it may cause Wernicke's encephalopathy, central pontine myelinolysis and death. In extreme cases, women may request, or their obstetricians recommend, termination of the pregnancy. There are uncontrolled data supporting a beneficial effect of corticosteroids in these women, and a randomised placebo-controlled trial is currently in progress.