The effect of betamethasone on fetal biophysical activities and Doppler velocimetry of umbilical and middle cerebral arteries.

OBJECTIVE: Preliminary reports suggest that antenatal steroid administration may confound the assessment of fetal well-being by suppressing biophysical activities, consequently drug-induced effects could prompt unwarranted delivery of premature fetuses. The purpose of this study was to examine the effect of antenatal betamethasone administration on fetal biophysical activities and Doppler flow indices of the umbilical and middle cerebral circulation. METHODS: Forty women at risk of premature delivery between 27-32 weeks gestation (mean 30.2 weeks) received two consecutive doses of intramuscular betamethasone, 24 hours apart. Ultrasonographic observations of fetal behavior for 30 minute periods and Doppler examination of the umbilical and cerebral arteries were performed prior to (0 hours), 48 hours after, and 96 hours after administration of the first dose. To account for fetal circadian rhythms and maternal prandial status, all examinations were carefully timed and performed between 1-4 pm. Analysis of Variance, chi-square test and Fisher's Exact test were used for statistical analysis, as appropriate. RESULTS: Nine patients were excluded from analysis due to delivery prior to completion of all examinations. Number of breathing episodes as well as total breathing time at 48 hours decreased by 83.0% (p<0.01) and 90.4% (p<0.01), respectively, at 48 hours in comparison to baseline. Fetal limb and trunk movements decreased by 53.2% (p<0.01) and 48.6% (p<0.01), respectively. Amniotic fluid volume and fetal tone were normal in all patients. At 48 hours, 14 of 31 fetuses and 4 of 31 fetuses had a biophysical profile score of 6/8 and 4/8, respectively, in comparison to 0 of 31 and 0 of 31 at 0 hours (p<0.05 and p<0.001, respectively). All parameters returned to baseline values at 96 h. Pulsatility indices of umbilical and middle cerebral arteries remained unchanged at 48 hours and 96 hours (p=NS). CONCLUSIONS: Betamethasone induces a profound, albeit transient, suppression of fetal breathing, limb and trunk movements, resulting in decreased biophysical profile scores. Awareness of this drug-induced effect might prevent unnecessary iatrogenic delivery of preterm fetuses.