Allergies in Pregnancy - impact on foetus and birth

Pregnancy is a time of intense change within the female body.  Hormonal changes have an influence on the immune system and allergic diseases may be affected by these changes. The hormones of pregnancy have  steroidal type effects and can also dampen down allergies.  In the pregnant state, the immune system is  down-regulated to prevent rejection of the foetus (which is immunologically a "foreign organism").  This increased immune tolerance has the positive spin-off of causing less direct reactivity to foreign substances.  However, the allergy triggering potential of the immune system may be heightened.  

What happens to existing allergies in pregnancy

Asthma for example may become worse with frequent attacks, it may even occur for the first time in pregnancy.  But paradoxically it may become less severe and easier to control during pregnancy.  Good Asthma control is important in pregnancy to maintain an adequate oxygen supply to growing foetus. Prematurity and low birth weight may result from poor asthma control in the mother. Most asthma drugs can be safely used in pregnancy and there is no evidence that there is any increased risk to the foetus.  We do however recommend the lowest possible doses of any medication sufficient to control symptoms in the pregnant mother.
 Nasal allergies often occur for the first time in pregnancy.  Pregnant mothers are prone to nasal blockage and irritating nasal symptoms and increased nasal discharge. This state of affairs seems to be triggered by the hormones present in pregnancy.
 Urticaria and allergy-like rashes are also common in pregnancy. One particular rash that is perculiar to pregnancy is the Pruritis and Urticaria Papules and Plaques in Pregnancy ( PUPPP syndrome).  This manifests with intensely itchy eruptions, particularly on the lower abdomen and upper thighs of the pregnant person.  After the birth, the rash rapidly disappears but is most debilitating during the last few months of pregnancy.  Eczema on the other hand often improves in pregnancy and this may  possibly  be due to the increase in the body's natural cortisone-like steroids that occur in pregnancy. 

Preventing allergies in the unborn

As far as the unborn baby’s health is concerned, the pregnancy and treatment thereof can have profound impact on the foetus’s health and predisposition to allergy.  We know that if the mother has allergies there is a 30% chance of her baby having an allergy.  If both parents have allergy, the baby’s risk increases to 60% and if both parents have the same allergy for example asthma, then the risk of allergy in the unborn baby reaches 80%.  Maternal smoking during pregnancy and the eating of allergy provoking foods in her diet in the last few months of pregnancy may encourage allergic diseases to develop in the baby. The evidence is still not convincing that diet in early pregnancy makes any difference.
 We know that unborn babies start to produce the allergy regulating IgE antibody from 20 weeks of gestation.  We used to measure Total Cord Blood IgE levels at birth as an indicator of possible allergy development, but this test is not very accurate, so is no longer used.
Smoking in early pregnancy is potent trigger for the development of allergies in the unborn baby and if the baby is born into a smoking household this risk increases. The month of birth is extremely important.  If a baby is born to allergic parents and the birth month coincides with the beginning of the pollen season, then there is an increased risk of nasal allergies and asthma. 
Reducing the risk of allergies in infancy
Plan Breast feeding carefully!  The best scenario is exclusive breast feeding with no top-up formula feeds and a mother who pays special attention to her own diet.  No half measures can tolerated!   Although Breast-feeding is the recommended form of infant feeding as it provides the best nutrients and immune protection, we must warn breast-feeding mothers to strictly avoid all allergy provoking foods in their own diet.  Traces of these allergy provoking foods can be found in the mother’s breast milk shortly after eating them and this could possibly lead to allergic sensitisation in the baby.  Also be careful not to use nipple creams that contain peanut (Arachis) or nut oil extracts, as these may also lead to nut  sensitisation in the baby.
 Paradoxically, a home environment that is meticulously sterile and contains no animals at all might actually promote allergy development in the newborn.  This is the basis of the “Hygiene Hypothesis”.  The “dirtier” the infants initial environment, the less likely that allergies will develop!  We find that babies born into large families, with early exposure to usual childhood viruses and those born on livestock farms are less likely to develop allergies.  Those born into families with only a few siblings and no exposure to dirt or animals or exposed to antibiotics early in life are more prone to develop allergies.  Early exposure to day care environments at a few weeks of age, may also reduce allergies.  There is no evidence that childhood immunisations promote allergy development.  Natural bowel germs called Lactobacilli (found in Natural Yoghurt) may have a protective effect.
 Special attention should be given to protecting the newborn from allergens, we recommend using liberal emollients such as Aqueous cream on the skin, avoiding perfumed soaps and all biological detergents.  Cotton clothing and mittens are preferable to synthetic and woollen clothes. Bath additives and bubble baths should be avoided only use products such as Oilatum in the bath.  Carefully read labels and avoid Vitamin and medications with colours added. Even herbal or Homeopathic medications should be viewed with suspicion, as these are possible sensitising agents. 

Do’s and Don’ts of Pregnancy in Allergy prone mothers

Pregnant mothers should:

  • Not smoke cigarettes and avoid passive smoking.
  • Avoid excessive alcohol
  • Avoid allergy provoking foods such as peanuts, nuts, sesame, eggs and fish.
  • Avoid excessive exposure to pets such as cats, dogs, horses and house-dust.
  • Continue to take regular prescribed Preventer and Reliever Asthma medication throughout pregnancy. The Reliever Beta Agonists actually help to relax the uterine muscles.  Medication such as aspirin, beta blocker medication and codeine are other possible allergy triggers.
  • Avoid all non-prescription drugs and vitamins that contain colourings or additives.
  • We recommend avoiding any allergy provocative procedures in pregnancy such as Skin Scratch  Testing or Desensitisation Immunotherapy.
  • Pregnant women should continue to exercise, eat a balanced diet and get plenty of sleep. 

Newborn babies should have:

  • Exclusive breast feeding for 6 months if possible
  • Avoid exposure to cow’s milk and formula milk unless hypo-allergenic formulas
  • Be exposed to normal childhood viruses
  • Avoid antibiotic treatment for viral illnesses unless essential
  • Avoid creams containing nut oils, perfume and additives
  • Avoid all processed baby foods and rather eat freshly prepared foods from the age of 6 months.
  • Avoid all exposure to cigarette smoke.
  • Immunisations should be given as usual.

 Dr Adrian Morris
November 2003 
© Surrey Allergy Clinic (UK), 2004
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