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The core concept behind fetal circulation is that fetal hemoglobin (HbF) [14] has a higher affinity for oxygen than does adult hemoglobin, which, together with the difference in partial pressure of oxygen, allows a diffusion of oxygen from the mother's circulatory system to the fetus.
The pathway of fetal umbilical venous flow is umbilical vein left portal vein ductus venosus inferior vena cava eventually right atrium.. This anatomic course is important to recall when assessing the success of neonatal umbilical venous catheterization, as failure to cannulate through the ductus venosus results in malpositioned hepatic catheterization via the left or right portal veins.
The unpaired umbilical vein carries oxygen and nutrient rich blood derived from fetal-maternal blood exchange at the chorionic villi.More than two-thirds of fetal hepatic circulation is via the main portal vein, while the remainder is shunted from the left portal vein via the ductus venosus to the inferior vena cava, eventually being delivered to the fetal right atrium.
A catheter may be inserted into one of the umbilical arteries of critically ill babies for drawing blood for testing. [6] This is a common procedure in neonatal intensive care, and can often be performed until 2 weeks after birth (when the arteries start to decay too much). [7]
The common cardinal veins, also known as the ducts of Cuvier, [1] are veins that drain into the sinus venosus during embryonic development. [2] [3] These drain an anterior cardinal vein and a posterior cardinal vein on each side.
Persistent fetal circulation is a condition caused by a failure in the systemic circulation and pulmonary circulation to convert from the antenatal circulation pattern to the "normal" pattern. Infants experience a high mean arterial pulmonary artery pressure and a high afterload at the right ventricle.
All of these cardiovascular system changes result in the adaptation from fetal circulation patterns to an adult circulation pattern. During this transition, some types of congenital heart disease that were not symptomatic in utero during fetal circulation will present with cyanosis or respiratory signs.
A fetal heartbeat can be detected at around 17 to 20 weeks of gestation when the chambers of the heart have become sufficiently developed. [20] During childbirth, the parameter is part of cardiotocography, which is where the fetal heartbeat and uterine contractions are continuously recorded.