Vascular network modeling reveals significant differences in vascular morphology in growth-restricted placentas

Abstract

Aim: To construct and examine models of the vascular networks using the technique of vascular corrosion casting in placentas collected from normal pregnancies and from pregnancies complicated by fetal growth restriction (FGR).

Methods: Twenty placentas were collected from normal term pregnancies (Group NP) and an equal number from pregnancies with idiopathic term FGR (Group FGR) and placental vascular network models constructed by perfusing an acrylic-based solution separately into the umbilical vein and arteries. Placental blood volumes and blood vessel characteristics (number of branches, diameter, and morphology) were then examined and compared.

Results: In placentas from Group NP, the veins branched five to seven times with a peripheral artery-to-vein ratio ranging from 1:2 to 1:3. In placentas from Group FGR, the veins branched only four to five times with an artery-to-vein ratio of 1:1 to 2:1 and increased evidence of nodularity and pitting of the vessel walls. The two groups showed significant differences in placental blood volume and in the mean diameters of umbilical veins and arteries. In Group FGR, significant positive correlations could be found between birth weight and placental volume, venous diameters, and select arterial diameters.

Conclusion: Vascular network models can be constructed from term placentas. Such modeling may provide novel insights and improve our understanding of the placental vascular system in both health and disease.

Keywords: Fetal growth restriction; Placenta; Pregnancy; Vascular corrosion casting.

Figure 1

Images of the fetal (A) and maternal (B) aspects of the placental vascular network in a representative placenta collected from a healthy normotensive pregnancy delivered at 38 weeks of gestation. Original magnification, ×1 . A separate image of the fetal aspect is shown under ×3 magnification (C). The umbilical arteries contain deoxygenated blood and are shown in blue; the umbilical veins contain oxygenated blood and are shown in red. 1, Grade 1 artery (umbilical artery); 2, Grade 2 artery; 3, Grade 3 artery.

Figure 2

Images of the fetal (A) and maternal (B) aspects of the placental vascular network in a representative placenta collected from a pregnancy complicated by fetal growth restriction (FGR) and delivered at 37 weeks of gestation. Original magnification, ×1. A separate image of the fetal aspect is shown under 3× magnification (C). The umbilical arteries contain deoxygenated blood and are shown in blue; the umbilical veins contain oxygenated blood and are shown in red. Note that there appear to be many fewer veins in this FGR placenta compared with a normal placenta (Figure 1). 1, Grade 1 vein (umbilical vein); 2, Grade 2 vein; 3, Grade 3 vein; 4, vacuolated changes; 5, nodular changes.