Steroid injections that are given to pregnant women at risk of going into labour prematurely, may increase the children's risk of developing emotional and behavioural problems later on, a new study has found.

Mothers who are at risk of giving birth prematurely are often given steroid injections to help the baby's lungs mature. These steroids mimic the natural hormone, cortisol, which is produced in the foetus during the late stages of pregnancy. By replicating the effects of natural cortisol, the risk of lung problems are reduced.

Lung problems can lead to life-threatening breathing problems and these are common in premature babies.

Some researchers have expressed concern that exposure to high levels of these steroids in the womb may affect brain development. A link between stress in pregnancy and ADHD (attention deficit hyperactivity disorder) has already been found. As cortisol is produced in the body as a response to stress, it has been suggested that cortisol may be responsible for this link.

"There are a lot of studies that have found links between stress in pregnancy and effects on children's mental health, especially ADHD, and this might be related to cortisol. (Steroid injections) mimic the biological reaction when the mother is stressed, so we wanted to see if babies who were exposed to this treatment are affected similarly in terms of mental health outcomes," the researchers said.

They looked at 37 children in Finland who were exposed to these steroid injections before birth and compared them to 185 children who were not. A much larger group of over 6,000 children was also studied to confirm the findings.

The study found that children who had been exposed to steroid injections in the womb had poorer general mental health at the ages of eight and 16 compared to the children who had not been exposed.

These children were also more likely to display symptoms of ADHD.

"This study suggests there may also be long-term risks for the child's mental health. Although this is the largest study so far to look at these risks, the number of children in our group who were exposed (to the steroids) was still relatively small. More studies will be needed to confirm the findings," the researchers said.

However, they emphasised that ‘the benefits of steroid treatment on immediate infant health and survival are well-established and outweigh any possible risk of long-term behavioural/emotional difficulties'.

"Parents who are concerned that their child may be affected by behavioural or emotional difficulties should in the first instance contact their GP for advice," they added.

Details of these findings are published in the journal, PLOS ONE.

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