The Effect Of Betamethasone On Middle Cerebral Artery Doppler Flow In Fetuses With Elevated Peak Systolic Velocities

INTRODUCTION: Administration of betamethasone (BMZ) has been shown to decrease the morbidity and mortality associated with preterm birth, and is given to patients with a variety of complications such as preterm labor, PPROM, fetal growth restriction, and alloimmunization, among others. As middle cerebral artery (MCA) Dopplers are used to monitor fetal hemodynamics in patients with many of these conditions, we sought to determine if administration of betamethasone is associated with changes in MCA Doppler parameters in fetuses with an abnormally elevated MCA peak systolic velocity (PSV). METHODS: A retrospective longitudinal study was conducted including women with a fetal MCA PSV greater than 1.3 MoM that had an MCA Doppler assessment within one week before and one week after betamethasone administration. Pre- and post-BMZ MCA PSV were compared using a repeated measures t-test. RESULTS: 20 fetuses met inclusion criteria with diagnoses of alloimmunization (13), parvovirus infection (3), fetal growth restriction (2), and twin-twin transfusion (2). The pre-BMZ PSV of 1.60±0.16 MoM was significantly lower than the post-BMZ PSV of 1.41±0.16 MoM (p < 0.0001). 13 of the 20 fetuses had a second post-BMZ MCA Doppler performed with a PSV of 1.5±0.24 MoM which was not significantly different from the initial post-BMZ MCA PSV (p=0.231). CONCLUSION: Our data suggest that maternal betamethasone administration lowers the MCA PSV in fetuses with an initially elevated MCA PSV. This should be taken into account when using MCA Dopplers to monitor fetal hemodynamics in patients receiving BMZ.