Updated 20 November 2014

Nausea, vomiting during pregnancy: Part 2

Good news for all moms-to-be: Researchers have finally started to investigate nausea and vomiting of pregnancy and have made suggestions regarding treatment. DietDoc takes a look.


Nausea and vomiting of pregnancy (NVP) can vary from mild symptoms to such severe manifestations (e.g. vomiting 5 or more times a day), that it is classified as "hyperemesis gravidarum". This is a condition that has plagued pregnant women for millennia and yet we still don’t know what causes it and what types of treatment can be used to alleviate the unpleasant symptoms.

Luckily researchers are starting to investigate NVP and have made suggestions regarding treatment which may assist pregnant women who are affected.

Contrasting theories

On the one hand, some researchers believe that NVP may paradoxically be linked to “a favourable outcome of pregnancy, including increased birth weight and gestational age”. In other words, despite the fact that the mother’s food intake can be seriously affected by constantly feeling nauseous and having to vomit, the babies of such mothers seem to weigh more at birth and get born at a later stage than the babies of women who do not suffer from NVP. 

Coad and coworkers (2006) speculate that this unexpected outcome may be due to women increasing their nutrient intaketo try and counteract the symptoms of NVP, or improving the quality of their diets, or reducing their energy outputs. The reduced nutrient intake may also stimulate the production of growth factors which improve metabolism or the function of the placenta.

Conversely other researchers in Finland point out that “A limited or unbalanced supply of nutrients in pregnancy may permanently change the physiology and metabolism of the foetus, increasing the later risk of chronic diseases such as coronary heart diseaseand diabetes” (Latva-Pukkila et al, 2009).

Recent studies of children born to mothers exposed to starvation because of famine and poverty, have found that babies who suffer from a lack of vital nutrients during gestation and for the first few years of life, are more prone to developing so-called ‘diseases of lifestyle’ (heart disease, diabetes, hypertension, metabolic syndrome and obesity) in later life. It is, therefore, possible that babies of mothers who are malnourished because of NVP, will also run the risk of suffering from these diseases when they grow up.

The Finnish Study

A study was, therefore, conducted at the University of Turku in Finland to compare the characteristics and dietary intake of mothers with and without NVP during the first 3 months of pregnancy and to track the growth of their children to the age of 6 months. A group of 256 pregnant women and their infants were included in the study. 

The following results were obtained:

  • Women who developed NVP were generally older and expecting their first child
  • 72% of the mothers experienced nausea and vomiting and 4.8% vomited more than once a day
  • Women with NVP had shorter pregnancies than those who did not suffer from NVP (this finding contradicts the theory that NVP is associated with longer gestation periods)
  • Encouragingly there was little difference between post-natal depression scores in the NVP group (11%) and the non-NVP group (9%).
  • Women with NVP gave birth to boys more often (56%) compared to women in the non-NVP group (40%)
  • Women with NVP ate less meat and vegetables, but more carbohydrates and sugar than the mothers without NVP
  • Because of the lower intakes of meat and vegetables mothers with NVP tended to have lower niacin and zinc intakes
  • No significant differences were found in the weight and length of the babies born to both groups of women

The researchers concluded that pregnant women who suffer from NVP need to receive counselling to eat a balanced dietto ensure adequate nutrient intake for themselves and their unborn children (Latva-Pukkila et al, 2010), but that basically NVP in the first trimester did not affect the size and growth of the babies .

It is important to note that the women in this study did not suffer from severe NVP for the entire duration of their pregnancies. Until further studies have examined the nutrient intakeand health of women and their babies when the mother develops hyperemesis gravidarum, we don’t yet know if the severe manifestation of NVP has a lasting effect on the physical and psychological health of mothers and their children, or not.

Iron-containing multivitamins and NVP

A Canadian study indicated that iron-containing multivitamins may aggravate NVP. A group of 97 pregnant women suffering from severe NVP were advised to stop taking prenatal multivitamins and to switch over to a folic acidor an adult multivitamin preparation or a chewable children’s multivitamin. Up to 67% of the women with severe NVP who stopped taking an iron-containing multivitamin preparation reported that their symptoms improved signficantly. The researchers concluded that women suffering from severe NVP should avoid prenatal multivitamin preparations that contain iron for the first 3 months of their pregnancies (Gill et al, 2009).

So if you suffer from severe NVP (nausea and vomiting up to 5 times a day), then it may be a good idea to talk to your doctor or dieticianabout a switch from the standard prenatal iron-containing multivitamins to a vitamin and mineral preparation that contains a lower dose of iron. Do not stop taking your prenatal vitamins and minerals without first informing your doctor or dietician so that they can help you select another source of iron. For example, good dietary sources of readily available iron include red meat, liver, fish, eggs, iron-fortified breakfast cereals, maize meal and wheat bread, and dried fruit.

The latest research indicates that mild NVP limited to the first trimester of pregnancy does not seem to cause serious nutritional insults to mothers and their babies. Additional research will have to clarify what the effect is when pregnant women suffer from hyperemesis gravidarum, but one study so far indicates that severe NVP may react favourably to changing from an iron-containing prenatal multivitamin preparation to other multivitamins which still contain iron but not at such high levels, or to obtain iron from the diet by eating foods that are rich in iron.

- (Dr IV van Heerden, registered dietician) 


(Coad J et al, 2002. Nutrient insult in early pregnancy. Proc Nutr Soc, Vol 61(1):51-9; Gill SK et al, 2009. The effectiveness of discontinuing iron-containing prenatal multivitamins on reducing the severity of nausea and vomiting of pregnancy. J Obstet Gynaecol, Vol 29(1): 13-16; Latva-Pukkila U et al, 2010. Dietary and clinical impacts of nausea and vomiting during pregnancy. J of Human Nutr & Dietetics, Vol 23, Issue 1:69-77)


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