Steroid injections given to pregnant women before premature birth may increase the child's risk of later behavioural and emotional difficulties, a study has found.
Mothers who are expected to give birth prematurely are often given an infusion of glucocorticoids, which mimic the natural hormone cortisol. This treatment is vital for helping the baby's lungs mature, but the new research suggests it may also increase the risk of mental health problems including attention-deficit/hyperactivity disorder (ADHD). ADHD is the most common behavioural disorder in young people in the UK.
The study, by researchers at Imperial College London and the University of Oulu, Finland, is published in the journal PLOS ONE.
Cortisol is produced in the fetus in the late stages of pregnancy to help the lungs develop, preparing the baby for life outside the womb. Lung problems are common in premature babies, and can cause life-threatening breathing difficulties. Synthetic glucocorticoids, which replicate the effects of natural cortisol, are given in anticipation of preterm birth to reduce the risk of these problems.
There has been some concern that exposure to high levels of glucocorticoids in the womb might have harmful long-term effects on brain development. Scientists have previously established a link between stress in pregnancy and symptoms of ADHD in children. As cortisol is produced as a response to stress, it has been suggested that cortisol may be responsible for this link.
The researchers studied 37 children who were exposed to synthetic glucocorticoids before birth and compared them to 185 children who were born at the same gestational age but did not have glucocorticoid treatment. A much larger comparison group of 6079 children, matched carefully on pregnancy and infant characteristics, was also examined to confirm the findings.
The children who had the treatment had poorer scores on general mental health at ages eight and 16, and were more likely to show symptoms of ADHD.
Alina Rodriguez, the senior author of the study, Visiting Professor at the School of Public Health at Imperial College London, said: "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.