NEW YORK (Reuters Health) - In terms of auditory neural maturation, repeat courses of antenatal betamethasone appear as safe as a single course for premature infants, New York researchers report in the March issue of Pediatrics.

A single antenatal course of corticosteroids may be inadequate to reduce risk of respiratory distress syndrome or patent ductus arteriosus in a fetus at risk of preterm birth, the authors point out, but multiple antenatal courses have been associated with a risk of delayed myelination of the central nervous system in animals.

To assess the safety of multiple courses of betamethasone on the central nervous system in the premature fetus, Drs. Sanjiv B. Amin and Ronnie Guillet of the University of Rochester, New York, conducted a retrospective cohort study of 79 premature infants born at that institution who received antenatal corticosteroids and who had auditory brainstem response testing done during the first 24 hours of life.

Fifty infants received one course of antenatal betamethasone and 29 received two or more courses. Perinatal demographics were similar between the two groups.

Drs. Amin and Guillet found no differences in absolute wave latencies, mean interpeak latencies or distribution of any response type between infants receiving a single course compared with those receiving multiple courses of betamethasone.

"The findings of our study suggest that multiple courses of betamethasone have no acute harmful effects on brainstem maturation as evaluated by auditory brainstem evoked responses," Dr. Amin told Reuters Health.

"The existing recent literature ... suggest(s) that the long-term adverse effect on developing brain may be specific to corticosteroid preparation and may not be associated with betamethasone."

There are differences "in both effectiveness and side effects, depending on whether betamethasone or dexamethasone is used," the Rochester investigator commented. "We specifically looked at betamethasone and did not identify adverse effects on brainstem development."

"The evaluations we did are specific to the brainstem," Dr. Amin cautioned. "Although we think the results can be generalized to the whole brain, we do not have data on other parts of the brain such as the cortex."

Randomized, double-blind studies are now needed to better assess the safety of multiple courses of betamethasone in the preterm infant, he concluded.