First-born children are at higher risk of developing asthma and allergy because of different conditions they experience in the uterus, according to new research from the Isle of Wight in the United Kingdom.

In order to determine whether the higher risk of asthma and allergy in first-born children is the result of a prenatal process of post-natal factors, researchers investigated whether birth order affected several immune markers that are set at birth, including a variation in the DNA of the IL-13 gene, which is linked to allergic development.

The Study

They recruited more than 1,200 newborns form the Isle of Wight and ascertained their birth order, then sampled their cord blood IgE, an indicator of allergic development, and conducted skin prick tests at ages four and 10. “This is the first study to test whether the effect of genes involved in the development of asthma and allergy differs between first- and later-born children,” said Wilfried Karmaus, M.D., M.P.H., of the University of South Carolina.

They found that among first-borns, the IL-13 gene variant was associated with a statistically significant higher relative risk of having increased cord-blood IgE, an indication of increased allergic response. This higher risk seemed to persist in older children; at four and ten the children with increased cord blood IgE were also more likely to have a positive skin prick test. Such associations were not found in children who were not first-born.

“We were not surprised that birth order had an effect on the development of the immune system, but were surprised that this interaction persisted at least through age ten,” said Dr. Karmaus.

This gene-birth order effect is indicative that genes act differently in first-born children. “Our findings add to the evidence that allergic reactions are programmed during pregnancy and then effect the disease in later life,” he added. “This finding may partially account for the increasing prevalence of asthma and allergies in children in the last 30 years, primarily seen in the western world, as developed nations’ birthrates continue to decline.”

It may also indicate that there are ways to reduce the chances of first-borns developing asthmaand allergy by changing the conditions in the uterus. “If we could produce pregnancy conditions for first-born children that are comparable to later-born children, we may be able to prevent 20 to 30 percent of all cases of asthma and allergy,” Dr. Karmaus concluded. “Better understanding the mechanism involved in prenatal priming [of immune development] may offer new and exciting avenues of intervention.”

About Asthma 

Asthma occurs when the main air passages of your lungs, the bronchial tubes, become inflamed. The muscles of the bronchial walls tighten, and cells in the lungs produce extra mucus further narrowing your airways. This can cause minor wheezing to severe difficulty in breathing. In some cases, your breathing may be so labored that an asthma attack becomes life-threatening.

Asthma is a chronic but treatable condition.

People with asthma experience symptoms when the airways tighten, inflame, or fill with mucus. Common symptoms of asthma include:

• Coughing, especially at night
• Wheezing
• Shortness of breath
• Chest tightness, pain, or pressure

Still, not every person with asthma has the same symptoms in the same way. You may not have all of these symptoms, or you may have different symptoms at different times. Your asthma symptoms may also vary from one asthma attack to the next, being mild during one asthma attack and severe during another. In fact, Some people with asthma may go for extended periods without having any symptoms, interrupted by periodic worsening of their symptoms called asthma attacks. Others might have asthma symptoms every day. In addition, some people with asthma may only have asthma during exercise or asthma with viral infections like colds.

Mild asthma attacks are generally more common. Usually, the airways open up within a few minutes to a few hours. Severe attacks are less common but last longer and require immediate medical help. It is important to recognize and treat even mild symptoms to help you prevent severe episodes and keep asthma under better control.

Asthma signs and symptoms can range from mild to severe. You may have only occasional asthma episodes with mild, short-lived symptoms such as wheezing. In between episodes you may feel normal and have no difficulty breathing. Some people with asthma have chronic coughing and wheezing punctuated by severe asthma attacks.