The human placenta : An angiographic study

Abstract: The arterial vessels from the umbilical cord spreading over the chorion and its cotyledonary branches constitute the main body of the placental vascular tree. In the present study it was visualized by angiography and related to placental developmental factors. The results were correlated with intrauterine growth and umbilical artery blood flow velocity waveforms (FVW). The association between FVW and placental morphology was investigated by angiography in 30 pregnancies at risk for intrauterine growth retardation (IUGR). Placentas from fetuses with an end-diastolic zero flow were small and thick with an extrachorial configuration, marginal cord insertion, magistral or mixed allantochorial vessel pattern and few cotyledons. The incidence and the extension of gross lesions were only slightly increased. The results show that placental developmental factors are associated with fetal growth and abnormal FVW. To further evaluate the arterial pattern, fractal geometry was accomplished and showed to be an applicable model. In 22 placentas from uncomplicated pregnancies with normal FVW, the scaling properties were as good as for constructed perfect fractals. The fractal dimension was in mean 1.864. The results suggest that there is an underlying regular mechanism behind the placental vasculogenesis. Sixteen placentas from SGA fetuses with pathologic FVW showed a significantly decreased fractal dimension (mean 1.755), indicating a lower grade of complexity. The anatomy of the frequent connection between the two umbilical arteries, Hyrtl s anastomosis, was investigated in 67 placentas from full term infants appropriate for gestational age (AGA) and in 64 placentas from infants small for gestational age (SGA). The anastomosis was constituted by a separate vessel in 112 placentas (85 %), a fenestration in 6 (5%) and a fusion in 3 (2%). In 10 the anastomosis was absent, in five of these due to a single umbilical artery. The anastomosis was wide in placentas in which the relative area supplied by each umbilical artery was asymmetric and thinner with a higher degree of symmetry. Placentas lacking anastomosis were highly symmetric. The occurrence and anatomy of Hyrtl s anastomosis seemed to depend on the demand on shunting between the umbilical arteries, and did not differ between placentas from AGA and SGA infants. The results show that the placental arterial pattern reveals abnormalities in early placental expansion and development and is linked with impaired fetal growth and pathologic FVW. The structure of Hyrtl s anastomosis is related to the size of the umbilical arteries supply areas proving its role as a shunting mechanism.