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BPS updates, Health and wellbeing

Nausea and vomiting in pregnancy

Brian L. Swallow looks at an unpleasant side of gestation.

28 March 2010

From the moment the patient enters hospital she is denied the solace of the vomit bowl. She is told that, in the event of not being able to control herself, she is to vomit into the bed; and the nurse is instructed to be in no hurry about changing her. … I assure them very dogmatically that they are going to stop vomiting at once… From the beginning they are put on full hospital diet, and their tray is in no way arranged to make them feel that they have digestive capacities other than normal (Atlee, 1934, p.757).

Treatment and support for women experiencing nausea and vomiting
in pregnancy (NVP) has improved significantly since this description from the 1930s. And yet there are even now a number of practitioners who attribute 'blame' to the woman for her sickness, such as anxiety or ambivalence towards the pregnancy. One of the most common frustrations for women is the feeling that their sickness is not taken seriously by others: they are unable to feel legitimately sick (Parker, 1997). This instils a sense of guilt and depression.

NVP is commonly referred to as 'morning sickness', but this term is, in fact, a misnomer (see 'Some common myths'). Fewer than 2 per cent of sufferers report experiencing it only in the morning (Lacroix et al., 2000). Most pregnant women experience nausea or vomiting at some time during their pregnancy, with some estimates as high as 90 per cent (Tierson et al., 1986). In any one week of early pregnancy we found between 30 and 40 per cent of women experience nausea either all the time or at least once a day (Swallow et al., 2002). Estimates for the most severe form of NVP, called hyperemesis gravidarum, are as high as1.5 per cent (Tsang et al., 1996).

Women feel desperate for relief

NVP reduces job efficiency, and an average of 62 working hours per woman is lost (O'Brien & Naber, 1992). It has a major impact on the woman's overall quality of life (Attard et al., 2002), well-being (Munch, 2002) and mental health (Swallow et al., 2004). Their families become anxious and fatigued with the additional support required (Parker, 1997).  

Symptoms may be so severe that women have impaired cognitive function and are unable to engage in even the most mundane activities, such as watching television or reading. They may become so desperate for relief from the symptoms that they request a termination of pregnancy. This is sometimes interpreted as ambivalence towards the pregnancy but is actually an indication of the degree of desperation felt by the woman (Nelson-Piercy, 1998).

I undertook a pilot study of four women diagnosed with hyperemesis gravidarum (Swallow, 2009), asking them to maintain daily diaries. They were also interviewed on a number of occasions during the course of their illness. Common themes emerged:

  • Isolation. Some women feel isolated and confined to their house, whereas others feel that they would like to be removed from the stresses of having to talk to other family members and friends. 
  • Confusion. Women are confused about why they are experiencing the symptoms. Their symptoms are not explained to them adequately; for example, 'I was just told I had to put up with it' and 'My doctor said it is because I am anxious'. 
  • Guilt. Women feel guilty – about not being able to prepare food, not being able to play with children, inability to undertake housework, and feeling a burden to partners and family.
  •  Support. Women with a supportive family rate their physical and mental health more positively, despite having significant symptoms of nausea. In contrast, woman without a supportive family structure are less positive in their ratings of mental and physical well-being. 
  • Nausea. Descriptions of nausea include: 'It is like nothing else I have experienced', 'It feels like my whole stomach is coming up', 'It is relentless', and 'I just wish I could be sick. I am sure it would be better than this constant nausea'. Most women think that the feelings of nausea are worse than the actual vomiting.   Food and odours. Women report that they cannot cope with preparing food. Food makes symptoms worse. It is better if food is prepared outside the home to avoid odours: 'Any smell makes me want to vomit, even the smell of Alex' (her son).

The enigma of NVP The causes of NVP are elusive. Physical explanations abound, but are inconclusive.

Research has focused on a range of theories. For example, NVP may be an evolutionary adaptive mechanism to avoid the ingestion of toxins and teratogens during the critical period of embryonic growth (Profet, 1992). Many common foods contain toxins that if consumed in large quantities may be harmful to either the mother or developing fetus; for example, potatoes contain mutagens called glycoalkoloids. NVP may be a result of either enhanced olfactory or taste mechanisms, or enhanced implicit memories of odours containing toxins. Some research lends support to the role of olfaction in NVP (Ochsenbein-Kolble et al., 2007), but our research failed to identify differences in olfactory sensitivity between pregnant and non-pregnant women (Swallow et al., 2005a).

Women report that food odours aggravate their symptoms (Alley, 1984). Our research (Swallow et al., 2005b) also identified odour, rather than taste, as the main perceived mechanism responsible for triggering NVP symptoms.

Cultural differences in the manifestation of symptoms have been identified. Flaxman and Sherman (2000) undertook an analysis of 56 studies from 16 countries. The overall mean incidence of NVP was 66 per cent. Japan reported the highest incidence (84 per cent), whereas India had the lowest (35 per cent). 

The authors also collated data from traditional societies and compared incidence with diets. Of the 27 traditional societies examined, 'morning sickness' was absent in seven (26 per cent). Only one of these seven societies included meat (potentially high in toxins) as one of their staple diets, whereas six had corn as staples. This data was used to support the evolutionary adaptive hypothesis: societies that do not experience symptoms are primarily those that are not exposed to food containing potential toxins.

This is convincing evidence for a socio-environmental factor in the manifestation of symptoms. However, variances of NVP measures are often greater between studies within a culture than those between cultures. This may be due to different methods employed to measure NVP, as there is no standard definition for either NVP or hyperemesis (Swallow et al., 2002).

One way to overcome this problem is to examine cultural variations within a society using a standard methodology throughout. One such study conducted in South Africa (Walker et al., 1985), compared incidence in 'Black', 'Coloured', 'Indian' and 'White' participants. There were lower frequencies for both NVP (56 per cent vs. 69 per cent) and hyperemesis (2.8 per cent vs. 12.2 per cent) for Black compared to Indian women.

The highest incidence of NVP for those from an Indian ethnic background living in an alien culture contrasts with the findings of Flaxman et al. (2000), who reported the lowest incidence for Indian women living in their own culture. Colleagues in other parts of the UK, who report a higher incidence of hyperemesis gravidarum in women from Indian subcontinent ethnic origins living in the UK, support these ethnic variations within a culture.

These findings may imply dietary differences or other socio-environmental factors, rather than physiological or genetic differences. It is possible to use this data to support an evolutionary hypothesis; alternatively a biopsychosocial paradigm may be developed, as in Figure 1. This shows a link between physiological factors and nausea and vomiting: women state that the physical sickness associated with pregnancy is so severe that a physical origin must be present. The physiological contribution is supported by research that suggests hormonal changes in women (Leylek et al., 1999). However, the possibility that nausea leads to changes in physiological measures, or that mediating variables are responsible for increased levels of hormones cannot be excluded. The dashed lines in the figure show these.

Social factors include social support, socioeconomic status, marital discord and negative life events. The main psychological relationship identified in our work was depression (Swallow et al., 2004), but we stated that depression was likely to be the result of NVP, rather than the cause. This conjecture is supported by recent longitudinal work (Bozzo et al., 2006). Other research has suggested relationships between self-esteem, personality disorders, immaturity, dependence, helplessness, anxiety and stress (Kuo et al., 2007).

In addition, there is a possibility of a classically conditioned response with the sickness and environmental cues. Research using rats supports the notion of taste aversion conditioning (Batsell & Batson, 1999). This may partly explain why pregnancy sickness is alleviated on hospital admission, when women are placed on saline drips and denied food, but recurs on their return home.


Nationally, there is no standard strategy for treating NVP or hyperemesis gravidarum. Some health trusts have developed local protocols for inpatient treatment of hyperemesis. Since the 1960s, there have been no licensed anti-nausea medications – a legacy of the prescription of thalidomide – although there are a number that are safe and effective. In Canada, however, women are treated aggressively with anti-nausea medication at the first signs of NVP, especially if they experienced it in an earlier pregnancy.

The box below lists some strategies for coping with severe NVP. A supportive relationship with carers, rest and a stress-free environment are all important factors to help control the symptoms.


On 28 December 1854 the pregnant Charlotte Brontë wrote in a letter to her friend: 'My health has been really very good… till about ten days ago, when the stomach seemed quite suddenly to lose its tone, indigestion and continual faint sickness have been my portion ever since' (Shorter, 1908, p.336). A few days later, her biographer Elizabeth Gaskell observed: 'But the dreadful sickness increased and increased, till the very sight of food occasioned nausea' (Shorter, 1908, p.336). Three months later, Brontë died. Whilst her death certificate states 'phthisis' (tuberculosis) it is more likely that she died from hyperemesis gravidarum.

Women now rarely die due to hyperemesis gravidarum. However, the psychological and social consequences of the condition are still significant for the woman and her family and there is still a pervading ethos that it is somehow the woman's fault. It is worth pondering whether more research and better support would have been developed if this condition had been one that afflicted men. 

The Universities of Lincoln and Warwick are organising the first conference into NVP for 10 years. It will take place at Warwick University on 1 July 2010. It is hoped that this will lead to a better understanding of the condition, better support and treatment, and more research that will assist women to cope with this disabling complication. One of the primary aims is to develop protocols for the treatment that can be applied on a nationwide basis. Contact me for details.

Box - Some common myths
Myth no 1: It happens in the morning.
No, it can occur at any time of day. It is as common in the evenings as it is in the morning.

Myth no 2: It happens to everyone.
No, but it depends on how you define pregnancy sickness. Half of women do not experience vomiting in pregnancy, although
90 per cent experience nausea.

Myth no 3: It is something that women just have to put up with.
For severe NVP it is essential that women receive care and support. Women need to be monitored for dehydration and if necessary admitted to hospital. Severe cases will require rehydration through a saline drip.

Myth no 4: It is not a serious problem.
For some women it is. Very severe nausea and vomiting used to lead to death. It has been described as like the stomach trying to turn itself inside out. 

Myth no 5: It occurs in women who are anxious.
In actual fact, the NVP causes the anxiety, not the other way round.

Myth no 6: Hyperemesis gravidarum occurs because the woman is ambivalent towards her unborn baby.
This Freudian explanation was arrived at by interviewing women who were severely sick and discovering, unsurprisingly, that they were not sure that they wanted to carry on with the pregnancy. The ambivalence is caused by the sickness, not the other way round.

Myth no 7: NVP is harmful to the baby.
There is no evidence to support this. Indeed, some research suggests that women who experience moderate nausea and vomiting have better outcomes – less likelihood of miscarriage and higher birth weight. Women who experience hyperemesis gravidarum may have a higher incidence of low birth weight babies and fetal abnormalities, but so long as women receive appropriate treatment this difference is not significant.

Box - Coping with severe sickness in pregnancy

  • Visit your GP at an early stage.
  • Ask your GP to monitor your hydration regularly. I
  •  Discuss with your doctor the possibility of taking anti-nausea medication (although many doctors are reluctant to prescribe them).
  • If taking medication, consider requesting suppositories if you have difficulty keeping oral tablets down.
  • Avoid odours, especially of frying food. Even faint smells can be troublesome. If possible, do try encouraging your partner to avoid cooking in the house.
  • Take plenty of rest and relaxation.    
  • Enlist help and support – someone to care for your other children; someone to do the household chores. 
  •  Do not feel guilty. It is not your fault.
  • Avoid stress.    
  • Try to maintain fluid intake, but eat only when and if you feel like it.   
  • For mild symptoms, some women report that ginger, acupressure (in the form of 'Sea Bands') and dry biscuits help. However, research is equivocal.

Dr Brian L. Swallow
is at the Department of Psychology, University of Lincoln
[email protected]


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