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Chorion

Medically reviewed by: Stephanie Curreli, MD, PhD
Last Updated: Jan 29, 2015

The chorion is a membrane which develops between the mother and the fetus in pregnancy; it grows around the fetus and around other membranes which protect the developing fetus. The chorion provides for nutrient, oxygen, and waste transfer between the mother and fetus via the chorionic villi, which grow out of the chorion and into the endometrium.