Effect of antenatal betamethasone therapy on maternal-fetal Doppler velocimetry

(I)ntroduction: The overall impact of betamethasone administration on fetal parameters includes a transient reduction in FHR variation and fetal body movements. An effect on maternal-fetal blood flow has also been hypothesize d. We aimed to evaluate this effect in third trimester high risk pregnancie s by means of color Doppler technology. Methods: Thirty-six high risk pregnant women were considered for this study (mean gestational age at first day of betamethasone administration was 30. 7+/-2.6 wks; min=27 wks, max=35 wks), Umbilical artery (UA PI), middle cere bral artery (MCA PI) and uterine arteries (Ut RI) flow-velocity waveforms w ere assessed 48 hrs before treatment, and 48 and 96 hrs after second dose o f betamethasone, administered to accelerate fetal lung maturity. Results: When we analyzed the seriated measurements of each Doppler velocim etry parameter for the whole study group, we found a statistical significan t difference between basal MCA PI values and MCA PI after 48 hours (p=0.004 ), and between MCA PI after 48 hours and after 96 hours from betamethasone administration (p<0.03). No difference was found for the other Doppler para meters evaluated. When we analyzed the Doppler serial measurements of the s ubgroup <32 wks' gestation, we found again a statistical difference between basal MCA PI and MCA PI after 48 hours (p<0.006) and between MCA PI after 48 hours and after 96 hours from betamethasone administration (p<0.05). Con versely, no difference was found when Doppler seriated measurements of the sub-group greater than or equal to 32 wks' were assessed. Interpretation: Betamethasone treatment is associated with an increase in e nd diastolic flow reflected in a significant, transient reduction of MCA PI , and this is significant at gestational ages <32 wks' gestation. The latte r suggests a temporal decrease in vascular cerebral resistance.