High levels of antibodies to allergens in a baby's umbilical cord blood might be more important in the development of childhood allergies and asthma than exposure to allergens, or lack of them, after birth, suggests research in Thorax.
The authors base their findings on more than 1300 children born between 1989 and 1990, from whom a sample of cord blood serum was taken at birth to measure levels of IgE, an immune system response indicating sensitisation to allergens, such as pet dander, house dust mite, and grass pollens.
The children were also assessed at the ages of 1, 2, 4 and 10 years of age to find out if they had developed allergies and/or asthma.
By the age of 4, one in five children had become sensitised to allergens, and by the age of 10 more than one in four (27%) had done so.
Children who had high umbilical cord blood levels of IgE at birth were around twice as likely to have become sensitised.
One in 10 of the children had been diagnosed with asthma by the time they were 1 to 2 years old; by the age of 4, one in seven (15.2%) of the children had asthma. Almost 13% of the children had asthma by the time they were 10.
High IgE cord blood levels were not associated with the development of asthma up to the age of 4, but children with high IgE levels in their umbilical cord blood were around 66% more likely to have a diagnosis of asthma by the age of 10.
Such a finding suggests a late onset type of asthma, say the authors, pointing out that this is backed up by the percentage of asthmatic children with high IgE rising by age, from just under 9% at 12 to 24 months to 18.5% by the age of 10.
Children who were not sensitised to allergens at any age were more than three times as likely to be diagnosed with asthma by the age of 10 if they had high IgE levels in their umbilical cord blood.
Exposure to pets at birth was not associated with cord blood IgE, nor did it explain the patterns of allergic sensitisation and asthma.
Dramatic changes in the immune system occur during pregnancy, and the immune response of the fetus can start as early as 10 weeks, say the authors. They suggest their findings indicate that fetal immune system programming could be more important than what happens after birth in influencing the development of childhood allergies
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