Background: The effect of antenatal betamethasone on fetal parameters includes a transient reduction of FHR variation and of fetal body movements. An effect on maternal-fetal blood flow has also been shown, with non-univocal results.
Aims: To evaluate the effect of antenatal betamethasone in third trimester singleton high-risk pregnancies by Doppler technology.
Subjects and methods: Thirty-six pregnant women who received a full course of betamethasone (12 mg i.m. two times, 24 h apart) were studied. The Doppler examination included the assessment of the pulsatility index (PI) of the umbilical artery (UA PI), the middle cerebral artery (MCA PI) and of resistance index of uterine arteries (Ut RI) before treatment, and 48 and 96 h after second dose of betamethasone.
Results: No significant variation was noted in UA PI through betamethasone therapy. MCA PI decreased significantly 48 h from the last injection of betamethasone (P=0.002), and returned to basal values at 96 h. No difference was found for the other Doppler parameters examined. When serial Doppler studies were analyzed according to the gestational age, in the group <32 weeks' gestation, MCA PI decreased significantly after 48 h (P<0.006) and returned to pre-treatment values after 96 h from the last betamethasone dose. Conversely, no difference was found in Doppler serial measurements in any of the analyzed districts in the subgroup > or =32 weeks.
Conclusion: Betamethasone treatment is associated with a significant, although transient, reduction of MCA PI, especially at gestational ages <32 weeks'.