Fetal hemodynamic changes following maternal betamethasone administration in monochorionic twin pregnancies featuring one twin with selective growth restriction and abnormal umbilical artery Doppler.

Objective:  To evaluate fetal hemodynamic changes following maternal betamethasone administration in monochorionic twin pregnancies featuring one twin with selective intrauterine growth restriction (sIUGR) and absence of end-diastolic velocity in umbilical artery (UA) Doppler.

Methods: sIUGR was defined as fetal weight below the 10th percentile in one twin and inter-twin birth weight discordance >25%. The results of Doppler examinations including UA, middle cerebral artery (MCA) and ductus venosus directly prior to (D0), at 24 h (D1) and 48 h (D2) after administration of the first dose of betamethasone were recorded. Cerebral-placenta ratio was defined as MCA pulsatility index (PI) divided by UA-PI.

Results: In four (20%) of the 20 cases, the UA Doppler of the growth-restricted twin returned to positive end-diastolic velocity after betamethasone administration. The UA-PI and MCA-PI of the sIUGR twin changed significantly after betamethasone administration: UA-PI was decreased at D1, the MCA-PI was reduced at both D1 and D2, and the cerebral-placenta ratio was not altered after betamethasone administration in the sIUGR twin.

Conclusions: The hemodynamic changes after betamethasone administration were different between the two monochorionic twin fetuses where one presented with sIUGR and absence of UA end-diastolic velocity. The etiology of a low rate of return of end-diastolic velocity in the sIUGR twin needs further evaluation.