Objectives: To compare the effects of maternal betamethasone and dexamethasone administration on fetal behaviour and fetal heart rate variation.
Design: A prospective randomised study of 60 women at increased risk of preterm delivery.
Outcome measures: Fetal heart rate and its variation, the incidence of fetal body and breathing movements.
Setting: Obstetric unit, University Hospital, Utrecht, The Netherlands.
Results: Following maternal betamethasone administration (day 2), fetal heart rate variation was reduced by 19% and fetal body and breathing movements by 49% and 85%, respectively. After dexamethasone treatment there was a significant increase in short term fetal heart rate variation (24%) on day 1. All values returned to baseline on day 4, indicating that no fetal deterioration had occurred during the course of the study period.
Conclusion: Betamethasone, with probably the greater beneficial effect, has more effects on fetal behaviour and fetal heart rate variation than dexamethasone. When assessing fetal condition, due account needs to be taken of these effects.