A study published in the February 2014 issue of the medical journal Annals of Allergy, Asthma and Immunology reports that a pregnant woman's exposure to infectious bacteria and viruses affects the uterine environment in ways that cause the baby to have a greater risk of developing allergies and asthma during childhood.
Researchers studied 513 pregnant women in Germany along with their 526 children. The mothers completed a questionnaire during pregnancy, when the child (or children) were at age 3 and then 12 months, and every year until the child's fifth birthday. In the families studied, 61% had at least one parent who had seasonal allergies, eczema, or atopic dermatitis.
Allergies and asthma are hereditary. If both parents have allergies or asthma, then the child has a 75% chance of developing one or both conditions. If only one parent has allergies or asthma, then the child has a 30 to 40% chance of developing one or both conditions. It neither parent has allergies or asthma, then the child has only a 10 to 15% chance of developing one or both conditions. This study found that mother who are exposed to "germs" during pregnancy bear children who have higher than expected odds of having allergies, asthma, or eczema by the age of 5.
How much higher?
- Children born to mothers who had breakouts of eczema during pregnancy were 75% more likely to have eczema by the age of 5.
- Children born to mothers who had breakouts of eczema during pregnancy were 111% more likely to develop seasonal allergies by the age of 5.
- Children born to mothers who had repeated colds during pregnancy were as much as 378% more likely to develop asthma by the age of 5.
- Exposure to dust mites increased the risk of asthma by 30%, but exposure to bacteria after birth lowered the risk of asthma by 22%.
Allergies, asthma, and eczema are conditions in which the immune system works overtime. If a child's immune system is programmed to fight infections while the child is still in the womb, it will tend to overreact to harmless substances in the environment after it is born. However, if a child's immune system is "busy" fighting bacteria, it is not as likely to develop allergies or allergy-like diseases.
Korean scientists have found that babies who have eczema and are then treated with probiotics containing Bifidobacterium spp. and/or Propionibacteria spp. bacteria were less likely to develop wheezing and asthma. Lactobacillus, the bacteria found in yogurt, is also helpful for preventing eczema and atopic dermatitis.
Giving babies probiotics, however, is not as successful in preventing allergies and asthma. Some clinical trials have found that they help, and other clinical trials have found that they do not. Since the objective of probiotic treatment is to "balance" the immune system, making sure that the white blood cells that make inflammatory chemicals are balanced by immune cells that make inflammation regulators, more is not better. Giving your baby a formula or food containing a probiotic once or twice a week is enough.
Other Reasons Pregnant Women Need To Avoid Infections
Infections during pregnancy affect more conditions in the child than just allergies, asthma, and eczema. Many other conditions in childhood and even adulthood are influenced by the mother's exposure to infections while the child is still in the womb.
- Exposure to influenza, rubella, or toxoplasmosis during pregnancy increase the risk the child will develop schizophrenia during late adolescence or early adulthood. However, some studies have found that breastfeeding, which passes the mother's immune factors to the baby, reduces the risk of future development of schizophrenia.
- In one study, a pregnant woman's exposure to lower respiratory tract infections during pregnancy was more detrimental for the baby's development of asthma than exposure to cigarette smoke. However, breastfeeding offset the detrimental effects of the mother's lower respiratory infections during pregnancy.
- "Stomach flu" during pregnancy, the viral kind, can increase the baby's risk of type 1 diabetes. However, introducing cow's milk before 3 months (that is, ending breastfeeding before the child has reached the age of 3 months) and introducing cereal before 6 months also increase the risk.
- Hepatitis B and hepatitis C can be passed from mother to infant in the uterus. Babies born to mothers who have hepatitis B should be vaccinated within 12 hours of birth so that they do not become chronic carriers of the disease. As many as 25% of babies who are not vaccinated at birth when they are exposed to the virus in the womb will eventually die of the disease. There are no vaccinations for hepatitis C, but only about 10% of mothers who have this form of viral hepatitis pass it on to their babies.
- Exposure to the H1N1 or H3N2 forms of influenza before birth affect the ways the baby's brain develops its neurons that make the neurotransmitter dopamine. When the mother gets these forms of the flu, the baby is at greater risk for diseases that are caused by imbalances in dopamine, such as schizophrenia and some personality disorders. Getting a flu shot, however, protects against the infection and does not cause the birth defect. Mothers who do not want to get the influenza vaccination should take careful precautions, such as frequent hand washing and careful cleaning of household surfaces during flu season, so they do not expose their babies to the virus.
- Laboratory studies with animals suggest that babies who are exposed to toxoplasmosis in the womb are more likely to develop gluten intolerance (celiac disease), causing severe reactions to wheat and other grains.
- Exposure of the mother to pin worms or hookworms before birth, or exposure of the child to pin worms and hookworms after birth, increases the risk of allergies to mites. Reactions to can cause both asthma and a form of acne known as rosacea.