Final answer:
Fetal circulation differs from postnatal circulation due to the unique prenatal environment. It includes circulatory shunts, relies on fetal hemoglobin, and utilizes the placenta for oxygen and nutrient exchange. Post-birth reconfiguration is necessary for the newborn's survival, while factors like IUGR and fetal viability are crucial to the infant's health.
Step-by-step explanation:
Key Factors of How Fetal Circulation Differs
Fetal circulation is notably different from postnatal circulation due to the unique conditions within the womb. Here are five key factors that illustrate how fetal circulation differs:
- The presence of circulatory shunts such as the ductus arteriosus, foramen ovale, and ductus venosus, which bypass the undeveloped organs like the lungs and liver.
- Exchange of oxygen and nutrients takes place through the placenta, rather than the lungs and gastrointestinal tract as it does post-birth.
- Fetal hemoglobin has a higher affinity for oxygen compared to adult hemoglobin, allowing for efficient oxygen transfer from the mother's blood to the fetus.
- The umbilical veins and arteries are crucial for fetal circulation, carrying oxygenated blood to the fetus, and returning deoxygenated blood to the placenta.
- After birth, these fetal structures must close and reconfigure to establish the separate pulmonary and systemic circulatory systems used during postnatal life.
In addition to these circulatory differences, factors such as intrauterine growth restriction (IUGR), birth weight, and fetal viability have significant impacts on the health of the newborn. IUGR can be caused by maternal, fetal, or placental factors such as placental insufficiency, contributing to low birth weight, a major risk factor for infant mortality.
Viability refers to the fetus's ability to survive outside the womb, which is significantly more likely after 26 weeks of gestation due to more developed respiratory and nervous systems.