With rates of allergy continuing to rise in most parts of the developed world, the factors driving the increase are still largely unknown. A large meta-analysis by researchers in South Australia has looked at the associations between birth weight (corrected for gestational age) and the incidence of allergic diseases.
Forty-two relevant studies were found, which included data from millions of people (primarily children) with allergic disease. Only those studies that corrected for gestational age or were restricted to full-term infants were included, to separate effects of foetal growth rates from those of prematurity.
A relative birth weight increase of 1kg was associated with a 44 per cent greater risk of food allergy in children, a 17 per cent greater risk of eczema in children, and a 34 per cent greater risk of eczema in infants up to 2 years of age. Risks of allergic rhinitis were not found to be associated with birth weight.
Because of the lack of studies extending beyond childhood, it is not known whether the relationship between increased birth weight and increased risk of allergy persists into later life.
It is also not yet known how birth weight influences the development of allergic disease.
Reference: Wooldridge et al. 2019. Journal of Allergy and Clinical Immunology. Doi: 10.1016/j.jaci.2019.08.032