Time‐interval analysis of ductus venosus flow velocity waveforms in twin‐to‐twin transfusion syndrome treated with laser surgery

ABSTRACT Objectives To investigate time‐interval variables of ductus venosus (DV) flow velocity waveforms (FVWs) in twin‐to‐twin transfusion syndrome (TTTS), comparing the results with reference ranges from normal singleton fetuses. The impact of laser surgery and the effect of prognostic factors were also evaluated. Methods In 107 TTTS cases, DV‐FVWs of both recipients and donors were recorded 1 day before and 2 days after laser therapy. Time intervals for systolic (S) and early diastolic (D) peaks were analyzed retrospectively with regard to acceleration time (acc‐S and acc‐D for S and D, respectively) and deceleration time (dec‐S and dec‐D for S and D, respectively). For each variable, Z‐scores were calculated with respect to previously reported normal reference ranges. Results Z‐scores for all variables showed statistically significant differences from those observed previously in normal fetuses, with the exception of dec‐S of donors. The most striking differences were observed in longer dec‐S of recipients (P