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

Objective. Preliminary reports suggest that antenatal steroid administratio n may confound the assessment of fetal well-being by suppressing biophysica l activities, consequently drug-induced effects could prompt unwarranted de livery of premature fetuses. The purpose of this study was to examine the e ffect of antenatal betamethasone administration on fetal biophysical activi ties and Doppler flow indices of the umbilical and middle cerebral circulat ion. Methods. Forty women at risk of premature delivery between 27-32 weeks gest ation (mean 30.2 weeks) received two consecutive doses of intramuscular bet amethasone, 24 hours apart. Ultrasonographic observations of fetal behavior for 30 minute periods and Doppler examination of the umbilical and cerebra l arteries were performed prior to (0 hours), 48 hours after, and 96 hours after administration of the first dose. To account for fetal circadian rhyt hms and maternal prandial status, all examinations were carefully timed and performed between 1-4 pm. Analysis of Variance, chi-square lest 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 to tal breathing time at 48 hours decreased by 83.0% (p<0.01) and 90.4% (p<0.0 1), respectively, at 48 hours in comparison to baseline. Fetal limb and tru nk 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 hou rs, 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 va lues sit 96 h. Pulsatility indices of umbilical and middle cerebral arterie s remained unchanged at 48 hours and 96 hours (p=NS). Conclusions. Betamethasone induces a profound, albeit transient, suppressio n of fetal breathing, limb and trunk movements, resulting in decreased biop hysical profile scores. Awareness of this drug-induced effect might prevent unnecessary iatrogenic delivery of preterm fetuses.