Placentomal development in the sheep and impacts of maternal obesity and overnutrition

The ovine placenta is comprised of four distinct placentomal types which progressively develop from type A, through types B, C, and D. It has been hypothesized that this progression of placentomal types increases placental efficiency, but little work has been done to satisfactorily explain these differences in terms of functional morphology. Further, maternal obesity and overnutrition during pregnancy results in fetal and placental overgrowth, but reduced placentomal angiogenic factor expression, at mid-gestation. Placentomal vascular growth is curtailed between mid- and late-gestation leading to reduced fetal growth and normal birth weight. Previously, no work had been done to evaluate the effects of maternal obesity on placentomal advancement. Here, we utilize corrosion casts of the fetal placental vasculature to analyze the three-dimensional microvascular morphology during placentomal advancement and the effects of maternal obesity on these changes.