Researchers have discovered that the size and growth rate of foetuses could act as an indicator of childhood asthma and allergies.
The link between the growth of a baby in the womb and its likelihood of developing asthma in childhood was found by a team at the University of Aberdeen, who did tests at various stages of pregnancy.
They also found links between the growth rate of unborn children and their chances of developing eczema and hay fever.
The team took foetal measurements of 1,500 pregnant women at Aberdeen Maternity Hospital during their first and second trimesters, at 10 weeks, then at 20 weeks gestation, and followed up with the children when they were aged 10.
A total of 927 families filled in respiratory questionnaires for their child and 449 children underwent lung function and skin prick testing, which looked for allergies to grass, eggs, dust mites and cats.
The results showed the children aged five and 10 who had asthma had been 5mm or 10% smaller than average as 10-week-old embryos.
The study revealed that an unborn baby smaller than the average foetus at 10 weeks and which remained small throughout pregnancy was five times more likely to develop childhood asthma.
Researchers also found a smaller than average foetus at 10 weeks which then grew to become a larger-sized baby was two-and-a-half times more likely to get eczema.
The results showed that a foetus which started off bigger than average at 10 weeks, but whose growth slowed resulting in them becoming smaller than average at a later stage, were more likely to be protected against hay fever.
Dr Steve Turner, who led the study, is a consultant with NHS Grampian and the clinical senior lecturer at the University of Aberdeen’s Department of Child Health.
He said: “Our main finding was that the shortest foetuses in the first trimester were at increased risk for persistent wheeze whereas the longest babies had better lung function at 10 years.
``We also found that changes in the expected growth rate were associated with altered risk for eczema and hay fever.
“In other words, initial foetal size and subsequent growth trajectory are important to respiratory and allergic outcomes in childhood.
“We already knew that the lungs develop in early pregnancy and that low lung function shortly after birth is a predictor of asthma and low lung function in adulthood, but this study finds evidence that the level of lung function and predisposition to asthma may be set shortly after mothers find themselves pregnant.
“However, foetal size is not the sole explanation for asthma. Asthma can have a different natural history in different children, for example some grow out of their asthma whilst some develop asthma as they reach secondary school age.
“But our study does give a better understanding of when asthma first begins in the many children who have symptoms throughout childhood.”
The team’s study is published in the American Journal of Respiratory and Critical Care Medicine.