Characteristics and outcomes of monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction with intermittent absent end diastolic flow.

Abstract

Introduction: Monochorionic diamniotic twins with selective fetal growth restriction (sFGR) are categorized based on the umbilical artery (UA) end diastolic flow (EDF) of the growth-restricted fetus. While persistent flow abnormalities are attributed to placental insufficiency, intermittent flow changes are often attributed to anastomoses. We hypothesized that not all intermittent flow is due to anastomotic fluctuation and sought to determine if pregnancies with intermittent forward and absent EDF may represent a unique cohort of sFGR pregnancy.

Methods: Retrospective analysis of prospectively collected data from a monochorionic pregnancy registry. Records of patients with monochorionic diamniotic twins with sFGR evaluated from January 2013 to December 2024 were reviewed. sFGR was defined by the Delphi-based consensus criteria. Pregnancies were grouped by the umbilical artery Doppler of the smaller fetus: (1) Type I: persistent forward EDF (+EDF); (2) Type II: no forward EDF (A/REDF); (3) Type IIIa: intermittent forward and absent EDF (iAEDF); or (4) Type IIIb: intermittent forward, absent, and reversed EDF (iAREDF). Pregnancy characteristics were compared between groups and outcomes were then compared in expectantly managed patients.

Results: Of 330 patients with sFGR, 114 (34.5%) had +EDF (Type I), 70 (21.2%) had A/REDF (Type II), 90 (27.3%) had iAEDF (Type IIIa), and 56 (17.0%) had iAREDF (Type IIIb). Gestational age at first evaluation was lower in those with Type II compared to Type IIIb (p = 0.003) and fetal intervention was higher in patients with any absent or reversed EDF compared to those with +EDF (p < 0.001). In expectantly managed patients (n = 189), median gestational age at delivery in weeks was higher in patients with Type I (32.5) and Type IIIa (32.4) compared to those with Type II (27.4) and Type IIIb (29.1) (Type I vs. Type II, p < 0.001; Type I vs. Type IIIa, p = 0.319; Type I vs. Type IIIb, p < 0.001; Type II vs. Type IIIa, p = 0.003; Type II vs. Type IIIb, p = 0.598; Type IIIa vs. Type IIIb, p < 0.001). Additionally, dual survival to discharge was higher in those with Type I compared to Type II (p < 0.001) but not compared to Type IIIa (p = 0.292) or Type IIIb (p = 0.262).

Conclusion: Patients with sFGR and intermittent absent EDF may represent a unique cohort with outcomes more similar to those with +EDF than those with intermittent forward, absent, and reversed EDF.