John: Hello, I'm John Hilton, editor of the Cochrane Editorial unit. Many pregnant women will experience some degree of morning sickness, but, for some, the nausea and vomiting will be much worse. Rupsa Boelig from the Thomas Jefferson University Hospital in Philadelphia, USA tells us about the findings of a May 2016 Cochrane Review of interventions to help them.

Rupsa: While nausea and vomiting in early pregnancy are very common, affecting approximately 80% of pregnancies, the severe form, hyperemesis gravidarum, affects only about one in a hundred. The definition of hyperemesis gravidarum varies but generally includes intractable nausea and vomiting, dehydration, electrolyte imbalances and weight loss. The onset is generally during the first trimester, peaking by 12 weeks, with most women feeling better by 20 weeks.
Although hyperemesis gravidarum is rarely a source of mortality, it is a significant source of morbidity. Beyond the maternal and fetal consequences of malnutrition, the severity of hyperemesis symptoms causes a major psychosocial burden leading to depression, anxiety, and even pregnancy termination. The socioeconomic costs of hyperemesis are also large, stemming from treatment expense, lost job productivity, and high healthcare costs. As providers of obstetric care, we struggle to care for these patients, to control their symptoms, return them to daily functioning, and keep them from being admitted and readmitted to the hospital. 
Our Cochrane Review set out to examine all interventions for hyperemesis gravidarum and to use randomized trials to evaluate their effects on nausea and vomiting, their safety for the mother and baby, and their economic costs. This review is unique in the breadth of the interventions examined and in its focus on hyperemesis gravidarum, rather than the more common and milder condition of nausea and vomiting in pregnancy. 
We identified a total of 25 studies involving a little over 2000 women for inclusion, but most of our analyses are based on data from single studies with small numbers of participants. The included studies covered a range of interventions such as acupuncture, techniques for outpatient care, and various pharmaceutical interventions. Overall, we judged the quality of the evidence to be low to moderate, limited by single studies and small sample sizes.
There was little high-quality and consistent evidence supporting any one intervention over any other, which is is important for people making management decisions who might be trying to choose between different interventions. In general, there were insufficient data on adverse maternal and neonatal outcomes, and larger studies are needed of the individual interventions if their safety is to be examined adequately.
While there were relatively few studies on non-pharmacological interventions, our finding from one study that midwife-led outpatient care had similar outcomes to inpatient hospitalization but with decreased hours in the hospital warrants further investigation, especially as we strive to limit the burden on both patients and the healthcare costs associated with hospital admission. 
The most commonly studied anti-emetics that were consistently found to be effective in managing hyperemesis were ondansetron, metoclopramide, and promethazine, with differences seen mainly in side effect profile. 
While larger studies should be done on these interventions, and on combinations of interventions, it is reassuring for both the providers of obstetric care and women with hyperemesis gravidarum to have a selection of interventions to choose from, and to be able to tailor their treatment regimen to their personal circumstances depending on side effect profile, safety concerns, and costs.

John: If you would like to find out more about the variety of interventions in the review, and to watch for future updates if new studies are done, the full review is available at Cochrane Library dot com and can be retrieved with a simple search for ‘hyperemesis’.