What Is the Role of the Placenta in the Fetal Development?

As a baby develops in the womb, the placenta develops in the womb, too. The placenta plays a crucial role for fetal well-being. Without a healthy placenta, positioned correctly in the uterus, the baby could not develop correctly. A physician will monitor the placenta as it supports the fetus 1.

Physical Attributes

An average full-term placenta has a diameter of 8.6 inches, a thickness of 1 inch and weighs about 1 pound, states physician Joseph F. Yetter III in “Examination of the Placenta,” published by American Family Physician 1. The placenta should have a dark maroon color with an umbilical cord attached. The average length of the umbilical cord is 23 inches and it has two arteries and one vein that fuse near the point where it connects with the placenta. The placenta develops and attaches to the uterine wall. As the uterus expands, the placenta grows and repositions itself in conjunction with uterine growth, according to the University of Maryland Medical System 24. The placenta should be in the top half of the uterus to ensure that it does not obstruct the cervical opening at the bottom of the uterus. If the placenta adheres near or covering the cervical opening, the mother has placenta previa. Because placenta previa can cause life-threatening bleeding, a physician monitors this condition closely.


During pregnancy, the mother’s body produces human chorionic gonadotropin in the blood and urine. This hormone sustains a healthy pregnancy. Human placental lactogen aids in fetal development and helps to stimulate milk glands for breastfeeding. Estrogen is also essential for the well-being of the pregnancy. The placenta produces these hormones continually throughout pregnancy, according to the Children’s Hospital of Wisconsin.

Nutrients and Oxygen

The placenta serves as an exchange spot for both maternal and fetal blood as it flows in and out of the umbilical cord, according to the American Pregnancy Association 13. Maternal blood flows through the placenta first as it moves to the umbilical cord, carrying the life-sustaining blood to the fetus. The baby receives nutrients through this blood. The baby also receives oxygen because the placenta exchanges oxygen and carbon dioxide with maternal circulation.

Blood Barrier

As blood moves through the umbilical cord, a blood barrier in the placenta prevents nutrients and oxygen from mixing with waste products that the fetus must eliminate, according to the University of Pennsylvania Health System 24. The blood barrier also filters out undesired particles from passing through the umbilical cord to the fetus.