Placental Weight, Shape and Gross Vascular Morphology

Abstract

The placenta is the only human organ that has a highly variable, stochastic shape. Deviation of a placenta from the average (more or less round, with a more or less centrally inserted cord and uniform disk thickness) reflects effects of the maternal environment on and the fetoplacental unit’s response to those stressors. That the majority of placental shapes are not round, not of uniform thickness and not with a central umbilical cord insertion speaks to the ubiquity of these stresses in even the most clinically uncomplicated pregnancies. It is for that reason that the placenta, as a marker or mediator of intrauterine effects, is so critical to the understanding of the fetal origins of adult health and disease, since the majority of us likely had some placental stress and potential programming that may account for aspects of our lifelong health.

Placental mass can be summed as “weight”, but chorionic surface shape, umbilical cord insertion relative to the shape of the chorionic plate and to the area of the chorionic plate covered by chorionic surface vessels, disk thickness and the structure of the chorionic surface vessel network have each significant and independent predictive value for birth weight and also vary with specific maternal and/or fetal disorders. Preliminary evidence also suggests that each of these placental gross features has a different, if slightly overlapping, critical period of development. We consider each of these below; for a summary of our approach, see https://www.youtube.com/watch?v=tWrPwaVUQ74&t=1967s.