Pregnancy Medication Use Found to Increase Risk of Childhood Asthma & Allergies

The prevalence of asthma and allergic diseases has significantly increased, particularly in children and young adults in the developed world during the last half century.

Research suggests that one of the reasons for this increase is prenatal exposure to certain medications which alters the natural immune development of infants and children.

A healthy immune system relies on strong barriers to environmental threats and a delicate state of immune cell balance.

When our physical barriers such as skin and mucosal tissues, also known as our innate (first line) immune defences are compromised, we are more prone to infections.

Similarly, when the immune cells that form our adaptive immune defences in response to specific antigens (foreign substances, infectious organisms or other immune threats), known as B cells and T cells are out of balance we experience symptoms of immune dysfunction.

T-cells are a major type of immune cell (lymphocytes) that work to seek and destroy specific immune threats once they have been recognised in the body.

Unfortunately, a number of environmental, genetic and lifestyle factors can cause this process can go awry and certain types of T cells become overactive, predisposing us to allergies or autoimmune conditions, depending on the cellular imbalance.

Immune Health in Infants and Children

For children, factors such as antibiotic use throughout infancy, method of delivery (vaginal birth/C-section), breast/formula feeding and nutritional status strongly influence immune health and T-cell balance.

New research shows that even before a child is born, their immune balance can be influenced in utero by their mother’s exposure to certain toxins and medications.

These exposures have been found to cause an increase in Th2 cells relative to Th1 cells, increasing risk of allergies such as eczema, hay fever, asthma, respiratory tract infections and candidiasis in the infant.  

 

Which Medications Have Been Studied? 

Paracetamol use during pregnancy has been found to be associated with increased risk of childhood asthma in numerous studies, however a causal relationship has not yet been established.

A recent meta-analysis of trials investigating this link concluded that the results of the review are consistent with an increase in the risk of asthma in children with a history of pre-natal exposure to paracetamol (Panadol) as well as both children and adults who have used paracetamol.

Researchers believe this may be due in part to a depletion of the essential antioxidant, glutathione as a result of Panadol use, contributing to immune dysfunction.

Antibiotic use in early childhood and maternally has also been found to influence the incidence of infant allergies.

Since infants who go on to develop allergic conditions have been found to have an altered immune response at birth and reduced gut microbial diversity, it is likely that prenatal factors influence the development of the allergic predisposition.

Researchers have found that prenatal exposure to antibiotics is associated not only with the increased risk of the child having persistent wheezing, but also with the development of hay fever and eczema, however, to a smaller extent.

It is believed that antibiotics have this effect on infant immunity (reducing Th1 and increasing Th2 allergy-promoting immune cells) as they reduce in utero exposure to infectious agents that play a role in developing natural immunity in early life.

Research also shows that antibiotic use in the immediate period after birth can significantly alter gut microbiota in infants, and evidence from long-term studies suggests that these disruptions to gut flora could last for months, if not years.

This is a serious problem, as the majority of the immune system lies in the gut, and gut microbial balance is required for healthy immune function and the prevention of allergic conditions.

Evidence is not yet conclusive on how the dose or timing of medication use pre-natally affects allergy risk in infants, however these factors are likely to make a difference and will require further research.

 

Further Reading: 

 

References

Azad, M.B. et al. 2011, Review Article: Perinatal Programming of Asthma: The Role of Gut Microbiota, Clinical and Developmental Immunology, Vol. 2012

Etminan, M. et al. 2009, Acetaminophen Use and the Risk of Asthma in Children and Adults: A Systematic Review and Metaanalysis, Chest Journal, Vol. 136(5)

Eyers, S. et al. 2011, Paracetamol in pregnancy and the risk of wheezing in offspring: a systematic review and meta-analysis, Clinical and Experimental Allergy, Vol. 41(4)

Jedrychowski, W. et al. 2006, The prenatal use of antibiotics and the development of allergic disease in one year old infants. A preliminary study, International Journal of Occupational Medicine and Environmental Health, Vol. 19(1)