Maternal dexamethasone and EEG hyperactivity in preterm fetal sheep.

Non-technical summary Long-acting glucocorticoids such as dexamethasone are commonly given to women at risk of preterm labour. While they significantly improve survival of the prematurely born infant, their effects on preterm brain activity is surprisingly unclear. We found that, in sheep, a conventional clinical course of maternal dexamethasone treatment was associated with dramatic, evolving low-frequency hyperactivity of the fetal EEG. This activity reflected a striking shift to less-frequent but higher amplitude EEG waveforms, and unexpectedly, EEG waveforms whose duration and pattern were highly consistent with seizure activity. After resolution of hyperactivity, the EEG showed changes consistent with maturation of sleep architecture, and reassuringly there was no histological evidence of brain injury 5 days after first exposure. The long-term implications are uncertain, but these effects may contribute to improved neonatal outcomes.