Placental characteristics in monochorionic twins with selective intrauterine growth restriction assessed by gradient angiography and three-dimensional reconstruction

Objective: To investigate the placental characteristics in selective intrauterine growth restriction (sIUGR) using gradient angiography and three-dimensional (3D) reconstruction from computed tomography (CT) scan data. Methods: This study included 23 sIUGR cases and 16 monochorionic twin-pregnancies without sIUGR. We injected nonionic iodinated contrast agents into the umbilical arteries and veins. Placental characteristics were analyzed after CT scanning and 3D reconstruction. Results: 73.9% of smaller twins in sIUGR cases had marginal or velamentous cord insertions and less placental sharing. The terminal branch of the arterial tree was scored III-IV in smaller sIUGR twins, while it was scored V-VII in normal monochorionic twins and larger sIUGR twins. Arterio-arterial (A-A) anastomoses presented in all monochorionic placentas. Veno-venous (V-V) anastomoses present in 83.3% (5/6) of Type III sIUGR cases, which was higher than observed in Type I-II cases. The mean diameters of A-A and V-V anastomoses were larger in Type III sIUGR cases. Conclusions: Gradient angiography and 3D placental models displayed different placental angioarchitectures and voluminal placental sharing among three types of sIUGR cases. Placental dysplasia in the smaller twin may cause abnormal cord insertion and unequal placental sharing. The inter-twin anatomoses influence the umbilical cord artery (UA) Doppler and natural pathogenesis of sIUGR.