The umbilical cord is clamped and the baby no longer receives oxygen and nutrients from the mother. With the first breaths of air, the lungs start to expand, and the ductus arteriosus and the foramen ovale both close. The baby’s circulation and blood flow through the heart now function like an adult’s.

The fetal circulatory system uses 3 shunts. These are small passages that direct blood that needs to be oxygenated. The purpose of these shunts is to bypass the lungs and liver. That’s because these organs will not work fully until after birth.

Blood flow in the unborn baby follows this pathway: Oxygen and nutrients from the mother’s blood are transferred across the placenta to the fetus through the umbilical cord. This enriched blood flows through the umbilical vein toward the baby’s liver. There it moves through a shunt called the ductus venosus.

The fetal circulation system is distinctly different from adult circulation. This intricate system allows the fetus to receive oxygenated blood and nutrients from the placenta. It is comprised of the blood vessels in the placenta and the umbilical cord, which contains two umbilical arteries and one umbilical vein.

Blood comes into the right atrium from the body, moves into the right ventricle and is pushed into the pulmonary arteries in the lungs. After picking up oxygen, the blood travels back to the heart through the pulmonary veins into the left atrium, to the left ventricle and out to the body’s tissues through the aorta.

And hence foetus take the oxygen and the nutrients for its growth from the placenta and the umbilical cord. The carbon dioxide and the other waste from the foetus pass to the mother and mix in her blood. Hence the lungs are bypassed in the foetal circulation.

As soon as the baby is born, the foramen ovale, ductus arteriosus ductus venosus and umbilical vessels are no longer needed.

From there, it moves into the left ventricle, which pumps the blood into the aorta. The aorta then delivers the blood to the body of the fetus. The remaining blood in the right atrium enters the right ventricle, which pumps it into the pulmonary artery, leading to the lungs.

Or the blood flow through the umbilical cord may be limited. Factors in both the mother and the baby may cause FGR. Factors in the mother that can cause FGR include: High blood pressure or other heart and blood vessel disease.

The fetus gets life support from the mother through the placenta. Waste products and carbon dioxide from the fetus are sent back through the umbilical cord and placenta to the mother’s circulation to be removed.

Foetal circulation (1)

• FETAL CIRCULATIONPresented by:A.
• INTRODUCTION:• The key to understand the fetal circulation is the fact that oxygen is derived from the placenta!
• Temporary structures in fetal period:Umbilical veinUmbilical arteriesDuctus venosusForamen ovaleDuctus arteriosus.

In a developing embryo,the heart has developed enough by day 21 post-fertilization to begin beating. Circulation patterns are clearly established by the fourth week of embryonic life.

In animals that give live birth, the fetal circulation is the circulatory system of a fetus. The term usually encompasses the entire fetoplacental circulation, which includes the umbilical cord and the blood vessels within the placenta that carry fetal blood.

Due to loss of tremendous blood flow through the placenta, the systemic vascular resistance at birth doubles. As resistance rises, aortic pressure increases. Furthur in pressure in left ventricle, left atrium increases as well. Due to expansion of the lungs, the pulmonary vascular resistance greatly decreases.

Which of the following describes an aspect of fetal circulation that does not occur in adult circulation? Both oxygenated and deoxygenated blood use the umbilical artery.

The high PVR during the fetal period is due to a combination of mechanical factors, various vasoconstrictor mediators, and relative hypoxemia. The fetal small pulmonary arteries have a characteristic cuboidal endothelium and thick muscular coat [10,11], which contribute to the elevated PVR.

While the majority of critical transitions occur in the first few moments after birth, circulatory and pulmonary changes continue for up to 6 weeks after birth. Transition is a time of significant risk to the newborn and necessitates astute observations on the part of the healthcare team.

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• Box 3-1: Transitional Period.
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• Second Stage (30 minutes to 2 hours): Period of Decreased Responsiveness.
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• Third Stage (2–8 hours): Second Period of Reactivity.
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• chapter 3: Newborn Transition: The Journey from Fetal to Extrauterine Life.