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Steroid medications may slow preemie brain development

For decades, steroid medications have been used to treat life-threatening complications in babies born prematurely. But now a study suggests the drugs – even in low doses – may impede brain development.

This isn't the first time that research has raised concerns about the widespread use of these medications in preemies. Previous animal studies have also indicated steroids may hamper brain growth. Even so, many pediatricians have assumed the drugs they would have no serious side effects if used in only small amounts.

The new findings, published in the journal Science Translational Medicine, are based on an assessment of 172 preterm babies at the UCSF Benioff Children's Hospital in San Francisco and the B.C. Children's Hospital in Vancouver. They were born at 32 weeks of gestation or less. (Full term is 37 weeks.)

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About 20 per cent of the infants were given small doses of glucocorticoids such as hydrocortisone or dexamethasone to help maintain normal blood pressure and speed up lung maturation in order to shorten time spent on breathing tube, which can lead to chronic lung disease.

Using high-tech MRI scans, the researchers measured brain volume and monitored the organ's growth. One brain scan was performed shortly after delivery. The second was done around the time the infant reached a gestational age of 37 weeks – or essentially when the baby should have been born.

The study revealed that, at the time of the second MRI scan, the region of the brain known as the cerebellum was about 10 per cent smaller in drug-treated infants compared to those not exposed to the steroids after birth. The cerebellum plays a key role in balance, motor skills, language and behaviour.

However, on a positive note, the study found that the brain was not hampered when a glucocorticoid called betamethasone was given to mothers in preterm labour. The drug appears to hasten lung development while the infant is still in the womb.

The researchers plan to follow the children until they reach school age in the hopes of determining the long-term consequences of impaired cerebellum growth in early infancy.

The study's results highlight the need for doctors to exercise caution when prescribing these medications to preemies, and when possible, to they should consider other treatments first, said the lead researcher, Emily Tam, a child neurologist at Benioff Children's Hospital. But she also stressed that "I would be hesitant to suggest that we do not use them at all, because we don't have good alternative treatments at this time."

What's needed, she said, are new therapies for treating preemies or ways to block the negative effects of glucocorticoids on the brain.

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