Young children given asthma medication before the age of two may not grow to their full height in later life, a preliminary report suggests.
The study of 12,000 Finnish infants found that, on average, those who used inhaled corticosteroids (ICS) long-term showed signs of stunted growth.
Previous research has suggested a link with growth suppression.
Experts said the study was a reminder that steroids should be used with caution in pre-school children.
However, Asthma UK said inhaled corticosteroids played a crucial in controlling asthma symptoms and reducing trips to hospital for young infants.
The findings are presented at the European Society for Paediatric Endocrinology conference.
One in 11 children in the UK has asthma, making it the most common long-term medical condition among children.
Inhaled corticosteroids (ICS) are strong medications commonly found in inhalers, used to treat asthma in adults and recurrent wheezing in children – but they are known to have side-effects in some people.
The latest guidelines for GPs recommend that all children taking inhaled steroids for asthma should have their height and weight checked every year for any signs of reduced growth.
Unclear who to treat
Lead researcher Dr Antti Saari, from the University of Eastern Finland, said his team had analysed information on the height of the children’s parents, as well as data on the children’s weight and asthma medicine, to calculate expected height and growth.
He found an association which, if permanent, could lead to around 3cm of decreased adult height.
Dr Saari said: “It is important that doctors think twice whether these steroids are needed or not in this age group.”
Jonathan Grigg, honorary medical adviser to the British Lung Foundation and professor of paediatric respiratory medicine at Queen Mary University London, said treating very young children who were wheezing was not easy.
“We haven’t worked out who responds to steroid treatment in this group. In young pre-school children who wheeze, it is unclear which ones should be targeted with steroids. Many grow out of asthma and won’t need further treatment.”
He said a larger study of different groups of younger children was needed to find out more.
Dr Samantha Walker, director of research and policy at Asthma UK, said inhaled corticosteroids were crucial for reducing and controlling asthma symptoms and the impact on height was “relatively minor”.
She added: “No parent should stop their children taking these life-saving medicines, because a slight reduction in growth is a small price to pay for medicines which may save your child’s life.”