Nausea and vomiting are common in the first trimester of pregnancy. In most women, these symptoms are self-limiting and usually tolerated. It is estimated that 70-90% of pregnant women experience nausea and 50% have at least one episode of vomiting or wretching. The thalidomide disaster drastically changed our perception of drugs’ effects on the fetus. Fetal exposure to thalidomide caused high rates of abnormalities (20-30%). Most doctors and pregnant women are over cautious with anti-emetics during pregnancy especially in the first trimester and they are generally avoided, unless vomiting is very severe. Therefore, not surprisingly, in recent years there has been increased interest in alternative therapies, which are perceived, at least by pregnant women, as safe. Randomised trials have demonstrated possible benefits for acupressure, pyridoxine and ginger but not for hypnosis.
Hyperemesis gravidarum occurs in around 0.1% of pregnancies and presents with severe and persistent nausea and vomiting leading to dehydration. Onset is usually in the first trimester (6-8 weeks gestation) of pregnancy. In addition to nausea and vomiting, there may be ptyalism (inability to swallow saliva) and spitting. The persistent vomiting may also lead to postural hypotension, tachycardia, electrolyte disturbances, ketosis, muscle wasting and weight loss.
Hyperemesis is a diagnosis of exclusion with no single confirmatory test. Therefore, other causes of nausea and vomiting such as urinary-tract infection, peptic ulceration, pancreatitis and rarely Addison’s disease must be considered. Hyperemesis usually recurs in subsequent pregnancies, so a previous history makes the diagnosis more likely.
The treatment of hyperemesis gravidarum requires careful hydration with normal saline and the earliest administration of high dose thiamine (150mg daily orally or 100mg weekly intravenously) to prevent Wernicke’s encephalopathy. Attention to nutrition is vital and occasionally TPN is required. Restoration of adequate nutrition usually improves liver biochemical abnormalities. There have been recent reports of the successful use of enteral nutrition.
Anti-emetics may play a part in the management of patients who do not respond to fluid and electrolyte replacement. Dopamine agonists (metoclopramide, domperidone), phenothiazines (chlorpromazine, proclorperazine) and antihistamines (cyclizine, promethazine) have all been shown to be safe. H2 receptor antagonists have been used occasionally with some benefit. The use of the 5-HT3 receptor blocker, ondansetron, has been reported in intractable hyperemesis although in one study it was shown to be no more effective than promethazine. In uncontrolled studies of intractable hyperemesis, corticosteroids have produced dramatic improvement. Recent reports showed the successful use of oral prednisolone (40-60mg daily) or intravenous hydrocortisone (100mg twice daily). In patients responding to steroid therapy, the dose must be reduced slowly and usually cannot be discontinued until the gestation at which the hyperemesis would resolve spontaneously, which may in extreme cases be at delivery. With appropriate management, the outcome of pregnancy in hyperemesis gravidarum is comparable to the general population.