Mechanisms and Treatment of Nausea and Vomiting in Pregnancy

Abstract

Nausea or vomiting in the early morning, so-called “morning sickness”, is so common that it is accepted as a symptom of normal pregnancy. Occurring soon after waking, it is often retching rather than actual vomiting and usually does not disturb the woman’s health or her pregnancy and the symptoms nearly always stop before the 14th week. In a much smaller proportion of cases, probably now not more than 1 in 1,000 total births, the vomiting becomes more serious and persistent, occurring throughout the day and even during the night. To this serious form of vomiting, the term hyperemesis gravidarum is given. It is difficult to find a definition of hyperemesis gravidarum in any standard obstetrics textbook and naturally one is faced with the problem: “when does the vomiting in pregnancy become serious enough to warrant the label hyperemesis?”. In 1956, the American Council on Pharmacy and Chemistry gave a lengthy definition restricting the term “nausea and vomiting of pregnancy” to the first 14–16 weeks and to cases showing no signs of disturbed nutrition. The term hyperemesis gravidarum was reserved for those few patients developing intractable vomiting and disturbed nutrition, with upset of electrolyte balance, weight loss of more than 5% or other more severe signs such as neurological disturbances, and liver or renal damage.