Incidence and characteristics of umbilical artery intermittent absent and/or reversed end-diastolic flow in complicated and uncomplicated monochorionic twin pregnancies.

Abstract

To evaluate the incidence and clinical relevance of intermittent absent and/or reversed diastolic flow on umbilical artery Doppler in different groups of monochorionic twin pregnancies. This was a prospective study involving three groups of monochorionic pregnancies: Group 1: controls followed fortnightly from the first trimester (n = 80); Group 2: cases with selective intrauterine growth restriction (n = 40); and Group 3: cases with severe twin-twin transfusion syndrome (n = 50). The presence and persistence over time of intermittent absent and/or reversed end-diastolic flow on umbilical artery Doppler was recorded. Placentas were examined and placental sharing and the presence of large arterioarterial anastomoses (AAA) was assessed. Perinatal outcome was recorded in all cases. Intermittent absent and/or reversed diastolic flow was present in 5% (4/80) of cases in Group 1, 45% (18/40) in Group 2 and 2% (1/50) in Group 3 (P < 0.0001, Group 2 vs. 1 and 3). Placental examination was performed in 76.4% (130/170) of cases and sharing was 58% for Group 1, 81% for Group 2 and 73% for Group 3 (P < 0.0001, Groups 2 and 3 vs. 1). Large AAA were identified in all examined cases with intermittent flow (18/18) and in 3.6% (4/112) of those without. The in-utero mortality rate was 0% in Group 1 and in Group 2 fetuses without intermittent flow. However, it was 19.4% in Group 2 cases with intermittent diastolic flow. Intermittent absent and/or reversed end-diastolic flow may be considered to be a characteristic sign of monochorionic pregnancy, and seems to result from the existence of large AAA. Its incidence is significantly increased in the context of selective intrauterine growth restriction, indicating a high risk for poor pregnancy outcome in these cases.