Effects of betamethasone on fetal heart rate

Objective. To evaluate the modifications provoked by betamethasone, used in prophylaxis for RDS, on fetal heart rate and variability. Materials and methods. Retrospective study including 58 pregnant women treated with corticosteroids for risk of preterm birth. Fetal heart rate and long term variability have been reviewed and evaluated with cardiotocographic examinations performed for each patient at time 0 (before betamethasone administration), within the first 12 hours after administration, between 12 and 24 hours, between 24 and 36 hours and after 36 hours. Results. Long term variability of fetal heart rate is altered above all in the period between 24 and 36 hours after the first administration of betamethasone (in the 48% of cases). This modification consists in the increase of variability in the 68% of cases. The baseline of heart rate shows a modification inversely proportional to the variability's one. Conclusion. The influence of corticosteroids on the fetal nervous centers involved in the regulation of the sleep-wake rhythm and in the sympathetic-vagal balance implies the possible transitory alteration of the fetal heart rate baseline and variability.