The accepted link between allergies and the environment in which we live has raised the question by some parents as to whether there is anything that they can do during the pregnancy to minimise the risk of allergies developing in childhood.
How do allergies develop?
In non-allergic people, the immune system effectively ignores substances such as pollen, food proteins, or house dust mite. However, in those with allergies, the immune system identifies these substances as threats and produces an inappropriate response against them.
Allergies are classified into IgE mediated and non-IgE mediated allergies.
In IgE mediated allergies, the immune system produces IgE antibodies specifically for that particular allergen. These antibodies alert the fighting cells (mast cells and basophils) within the immune system to watch out for the substance in the future. This is called sensitisation, and at this stage there are no physical symptoms of an allergy.
The next time that the same allergen is encountered, various cells of the immune system, including mast cells, identify it as an intruder and produce histamine and other chemicals. It is these chemicals which cause allergic symptoms.
The next time that the same allergen is encountered, various cells of the immune system, including mast cells, identify it as an intruder and produce histamine and other chemicals. It is these chemicals which cause allergic symptoms.
However, the immune system can still respond to allergens without the production of the IgE antibody. In non-IgE mediated allergies multiple cells may inappropriately react to the presence of an allergen, and can cause many of the same symptoms as IgE mediated allergies.
Once an allergy has been diagnosed the logical approach is to reduce exposure to the allergen which will reduce the risk of symptoms. It is logical to think that for children, whose immune systems are still developing, it is best to reduce the exposure to these substances which are common causes of allergy, in the first place.
This has raised the question of whether pregnant women should also minimise their exposure to potential allergens, thereby protecting their unborn child.
Pregnant women will always be particularly interested in finding out if there is anything they can to do reduce the possibility of their baby going on to develop allergies. While research is being carried out to look into all the possible causes of childhood allergy, current studies suggest that there is very little that can be done while pregnant that will influence the likelihood of allergies during childhood. However the current advice on the best steps to take for the health of the mother and baby are outlined below.
The best advice
The most important advice that pregnant women can put into action is to take care of their general health and to eat a healthy, balanced diet.
Diet
For every pregnant woman, doctors stress the importance of having a nutritious diet. Questions as to whether certain foods should be avoided due to the possibility of causing allergies once the child has been born continue to be investigated. However, avoiding potential food allergens in pregnancy has not been shown to reduce the risk of allergic disease in large, well-organised trials.
Peanut allergy, in particular, is of great interest to researchers and those looking at how to prevent food allergies. The number of children suffering from peanut allergy has almost doubled in the last two decades. While medical research is looking into this area, there has so far been no good evidence that any childhood allergy is caused by eating the ‘wrong’ foods, and thereby exposing the unborn child to allergens.
Most doctors therefore discourage mothers from avoiding potential allergens, because of the absence of evidence and the risk that, by doing so, mothers may be putting themselves and their unborn baby at risk due to not eating a diet sufficient in nutrients and energy.
In August 2009, the Government revised its advice to consumers about eating peanuts during pregnancy, breastfeeding and the first few years of life, in relation to the risk of developing peanut allergy in childhood. Until then, women had been advised to avoid peanuts during pregnancy and breastfeeding if there was a family history of allergy.
The new advice is that you can, if you wish, eat peanuts or foods containing peanut as part of a healthy balanced diet, unless you are yourself allergic to them. This applies during pregnancy and while breastfeeding.
The Government is currently funding a number of studies on peanut and other food allergies, with the aim of improving understanding of how and under what circumstances these conditions develop. It is hoped that these and other studies will provide more conclusive evidence in the future.
Allergy UK receives regular updates on new studies and the results of completed ones. This information, where it involves new guidelines on allergy management and prevention, will be available on the Allergy UK website as we receive it.
Meanwhile, eating a healthy diet that includes at least five portions of fruit and vegetables a day is straightforward, familiar guidance for healthy eating in pregnancy – healthy eating for both mother and baby. At the moment, it is the only definite advice that can be offered about diet in pregnancy with proven benefits to a child’s future health. More information can be found here.
If there are already a number foods that you are avoiding due to your own allergies, then it is wise to ask to be referred to a dietician (which you can arrange through your GP), particularly if you are at all concerned that you may not be getting the nutrition you need while pregnant or breastfeeding. Certainly, this is essential if you are excluding key food groups such as dairy or wheat, to ensure that you and your baby are not at risk of nutritional deficiencies. A dietician can direct you to alternatives that will provide the nutrition you need at this important time.
Extra nutrition
A key area of current research is that of the allergy prevention properties of certain foods. Some studies have shown that certain fish oils may have an allergy prevention effect; however, there are no guidelines at the moment regarding specific supplementation to aid allergy prevention. It is important to be aware of your total intake of oily fish during pregnancy. It is advised that you do not take more than two portions of oily fish a week. If you do decide to take a fish oil supplement, do not take fish oil supplements where they contain vitamin A (such as cod liver oil), as too much of this has been shown to be potentially harmful to the unborn child.
Fruit intake during pregnancy is important, and in some studies insufficient intake has been suggested to increase the likelihood of asthma up to the age of two years. There has been some evidence to show that apples, in particular, may help protect against breathing problems in young infants. However, at present there is not enough information available to consider if antioxidants from the fruit may have a protective influence while the baby is in the womb.
Other studies have suggested that if a mother’s diet does not have sufficient amounts of vitamin E then there could be a risk for asthma development in children from birth to the age of five years.
A good supply of fresh fruit and vegetables should be eaten throughout pregnancy to ensure adequate vitamins and minerals. As the studies mentioned above have yet to be corroborated, eating vast quantities of fruit, fish or vitamin E in the hope that your child will be allergy-free is not sensible, and consuming too much of one food may be harmful. If you ensure that you consume the recommended daily amounts of these foods, then you will have the required intake of the substances mentioned in these studies.
A good supply of fresh fruit and vegetables should be eaten throughout pregnancy to ensure adequate vitamins and minerals. As the studies mentioned above have yet to be corroborated, eating vast quantities of fruit, fish or vitamin E in the hope that your child will be allergy-free is not sensible, and consuming too much of one food may be harmful. If you ensure that you consume the recommended daily amounts of these foods, then you will have the required intake of the substances mentioned in these studies.
However, as with all the research mentioned here, further studies are needed before the Department of Health can make qualified recommendations on alterations to your diet. General nutrition information on what foods should be eaten, or avoided, during pregnancy can be found on the Government’s website here.
Smoking
Smoking when you are pregnant has many well-known health risks for your baby. Over 4,000 different chemicals are produced from smoking a cigarette. These chemicals go into the smoker’s body, and, in particular, the poisonous gas, carbon monoxide travels into the bloodstream and cuts down the oxygen that reaches the baby. The NHS states that, “For every cigarette you smoke, the blood flow to your baby is disrupted for about 15 seconds.”
In terms of allergy, several studies have shown that babies are more likely to develop wheezy breathing and asthma if their mothers smoked whilst they were pregnant. This may be to do with the fact that these babies are underweight, and their lungs are less well developed. Whilst this does not relate directly to allergy, less developed airways in these babies will be even more affected than usual if they go on to develop allergy.
Research has also suggested that, once born, at-risk babies (those born into a family with a history of allergy) who live with the second-hand effects of smoking have a higher rate of allergy (allergic rhinitis – constant runny nose), by the time they are 12 months old when compared to children in smoke-free households.
As a general rule, it is sensible to avoid both smoking and smoky atmospheres whilst you are pregnant and after your baby is born. In this way, you may be safeguarding your baby against the development of breathing problems at a later date, and protecting them from the irritant effects of tobacco smoke. That said, it appears that the most damaging effects of smoking on the unborn baby happen between four and nine months of development. If you can stop smoking within the first three months of pregnancy, then this may reduce, in part, the effect of smoking on the baby.
We know that giving up smoking, even when pregnant, is hard. There is a lot of support now for anyone wishing to quit smoking and it is sensible to use all the support you can get. You can approach your GP or midwife for advice, and the NHS now runs free stop-smoking clinics in all areas. These clinics are often based at GP practices; the staff involved are non-judgemental and hugely determined in supporting you in the move to stop smoking.
The NHS Smoking Helpline can be accessed by calling 0800 169 0 169 (7.00am to 11.00pm) and the Specialist Pregnancy Advice helpline is on 0800 169 9 169 (12.00noon to 9.00pm). This is currently only available in England; however literature packs are available upon request. More information on stopping smoking can be found at: http://www.nhs.uk/smokefree
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Key Points
- There has been no convincing evidence that childhood allergy is caused by eating the ‘wrong foods’ while pregnant
- The Department of Health advises that pregnant women can eat peanuts and foods containing peanut if they wish to do so, as long as they themselves are not allergic to peanuts
- Pregnant women should eat a healthy diet that includes at least five portions of fruit and vegetables a day
- Do not take supplements of fish oil containing vitamin A (such as cod liver oil), as these can be potentially harmful
- Avoid alcohol while pregnant, or drink no more than two units one or twice a week
- Smoking while pregnant poses serious health risks to mother and baby
- Smoking while pregnant can make the symptoms of allergies that children later develop more severe
- Use NHS stop smoking clinics and ask for help from your GP to support your aim to quit smoking
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