Thursday September 9 2010
Morning sickness is unpleasant but mostly harmless
“Morning sickness has no cure,” The Independent reported. The newspaper said that a new review of 27 past trials found that none of the treatments examined were safe and effective.
The review behind this news, conducted by the Cochrane research organisation, investigated a range of treatments for nausea, retching and vomiting in early pregnancy. The review, which looked at research on both anti-sickness drugs and alternative treatments such as ginger and acupuncture, found that there was a lack of high-quality evidence to support their effectiveness or safety. It should be noted that the body of evidence was found to be inconclusive rather than proving that there is “no cure”, as The Independent claimed.
In short, there is presently little reliable evidence to help pregnant women or doctors choose treatments for nausea and vomiting in pregnancy. This review specifically excluded studies that looked at treatments for more severe morning sickness (hyperemesis gravidarum), which can cause dehydration, vitamin and mineral imbalances, weight loss and other complications. Any pregnant woman whose wellbeing is affected by nausea and vomiting should consult her doctor or midwife.
Where did the story come from?
This Cochrane review was carried out by researchers from Dublin City University, the University of Liverpool, Indiana University School of Medicine and Mid-Western Regional Maternity Hospital, Limerick. It was funded by the University of Liverpool, Ireland’s Health Research Board and the UK’s National Institute for Health Research. The study was published online by the Cochrane Collaboration.
The review was widely covered by the media. Metro’s headline that pills for morning sickness are “useless” and the Daily Mail’s message that “none of them work” are misleading. Rather than clearly disproving the effectiveness of morning sickness treatments, the review found that there was very little evidence as to whether or not they worked, making it difficult for researchers to draw conclusions either way.
What kind of research was this?
This was a systematic review of all the evidence so far on treatments for nausea and vomiting in early pregnancy. A systematic review is the best and most reliable form of evidence for assessing healthcare interventions. In the process, researchers carry out a thorough search of the literature addressing a specific question and then critically appraise all individual studies to identify relevant evidence. This review is an update of a Cochrane review previously published in 2003.
The researchers point out that nausea, retching and vomiting are common in early pregnancy and can have considerable physical and psychological effects. Concerns over how unborn children may be affected by pharmaceutical treatments have led to more interest in complementary and alternative treatments, including acupressure, homeopathic remedies and herbal remedies such as ginger. Alternative treatments are often recommended by health professionals because they are perceived as “natural” and, therefore, safe. However, non-drug treatments are less rigorously regulated and, as a consequence, their potential risks may be underestimated. Doctors sometimes prescribe anti-emetic (anti-sickness) drugs and certain antihistamines.
What did the research involve?
Researchers carried out a search on various databases for all randomised controlled trials of any intervention for nausea, vomiting and retching in early pregnancy. This was defined as up to 20 weeks’ gestation. They excluded trials of interventions for severe morning sickness (hyperemesis gravidarum), as well as partially randomised and crossover trials (where different groups swap treatments within the same trial).
The researchers then examined evidence on whether treatments had been found to reduce symptoms or stop them getting worse, as measured by various validated scales and questionnaires. They also looked for information on adverse outcomes (side effects) on both mother and unborn baby, including foetal death and abnormalities, low birth weight and preterm birth. They also assessed information about how treatments affected quality of life and any economic costs, including purchase of treatments and time off work needed.
After all the data were collected, the reviewers independently assessed the studies to decide if they were suitable to be included in the review. Using established criteria, the researchers assessed the included studies for their quality, in particular their risk of bias. Researchers also analysed the effects of treatments using validated methods.
What were the basic results?
The researchers identified 27 trials, involving 4,041 women, that met their inclusion criteria. The trials covered many different treatments, including acupressure, acupuncture, ginger, vitamin B6 and several anti-emetic drugs. Overall, they found there was a lack of high-quality evidence on the effectiveness of any of the interventions. Although some studies showed benefits, the effects were inconsistent and limited.
The review included the following findings:
- Acupuncture and acupressure showed no significant benefit to women in pregnancy. In six studies of acupressure and two of acupuncture, there were no significant differences in benefit between women taking these treatments and women in a control group. One study of acustimulation (mild electrical stimulation of acupuncture points) reported some improvement.
- There was some evidence for the effectiveness of auricular pressure (gentle pressure on the outer ear), but further research on this treatment is required.
- The use of ginger products may be helpful, but evidence of their effectiveness was limited and inconsistent.
- There was only limited evidence to support the use of drugs such as vitamin B6, anti-emetic drugs and antihistamines.
- Importantly, little information was available on possible adverse outcomes and on psychological, social and economic outcomes. Some anti-emetic drugs were associated with drowsiness, while ginger was associated with heartburn in some people.
- The researchers did not find any trials of dietary or other lifestyle interventions.
Critical appraisal of the studies revealed that some had a high risk of bias, which would make results unreliable. Also, the researchers were unable to pool together findings from the studies to give an overall idea of effectiveness. This was because the studies differed in their methods, inclusions and ways of measuring symptoms. The researchers say that the methods used to carry out the studies were also of mixed quality.
How did the researchers interpret the results?
The researchers said that they found little strong evidence that non-drug treatments are effective in reducing symptoms of nausea and vomiting in early pregnancy. There was only limited evidence to support the use of vitamin B6, antihistamines and other anti-emetic drugs.
They concluded that there is little evidence to support any advice given to pregnant women about these interventions and that high-quality research on treatments for this condition is needed.
This well-conducted review found little evidence for the effectiveness of any treatments for nausea and vomiting in early pregnancy, in particular alternative treatments. Importantly, it also found little evidence about possible adverse effects of these treatments, many of which can be bought over the counter or are given by private practitioners. Further good-quality research is needed before pregnant women can make informed choices about treatment for morning sickness or before health professionals can offer evidence-based advice to support them.
In summary, there is currently little reliable evidence on which women and health professionals can base their decisions about treatments for nausea and vomiting in pregnancy. It is important to note that morning sickness can be severe, and this review specifically excluded studies that looked at treatments for more severe morning sickness (hyperemesis gravidarum). This condition can be associated with dehydration, vitamin and mineral imbalance, weight loss and other complications.
Any pregnant woman who experiences nausea and vomiting that affects her wellbeing should consult her doctor.