Fetal Physiology and Pathophysiology

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Questions and Answers

What type of deceleration is characterized by a rapid fall in heart rate with a rapid recovery to baseline?

Late deceleration

Early deceleration

Variable deceleration (correct)

Prolonged deceleration

Which deceleration pattern is a mirror image of uterine contractions and does not indicate hypoxemia?

Early deceleration (correct)

Variable deceleration

Late deceleration

Prolonged deceleration

What physiological process primarily contributes to chemoreceptor reflex decelerations?

Increased fetal systemic blood pressure

Accumulation of carbon dioxide and metabolic acids (correct)

Uterine contractions without blood loss

Decreased resistance in umbilical arteries

Which type of deceleration is likely to indicate fetal hypoxemia?

Late deceleration Signup and view all the answers

What is the duration of a deceleration for it to be categorized as prolonged?

More than 3 minutes Signup and view all the answers

What is the primary function of the placenta during fetal development?

To act as the lungs for gas exchange Signup and view all the answers

What happens to the pH of blood returning to the fetus via the umbilical vein?

It decreases due to accumulation of CO2 Signup and view all the answers

During normal labor, what effect do contractions have on maternal blood supply to the placenta?

They reduce blood supply to the placenta Signup and view all the answers

What can occur if CO2 cannot pass freely to the mother during labor?

Respiratory acidemia in the fetus Signup and view all the answers

What compensatory mechanism does the fetus utilize under conditions of low oxygen supply?

Increased affinity of fetal hemoglobin for oxygen Signup and view all the answers

What is the consequence of a reduction in oxygen supply during labor?

Centralization of blood flow to vital organs Signup and view all the answers

What role do catecholamines play during fetal distress?

Constrict peripheral blood vessels to prioritize vital organs Signup and view all the answers

What is the effect of chronic impairment of placental circulation on the fetus?

Severe bradycardia Signup and view all the answers

How does the fetus adapt to poor intrauterine nutrition?

By reducing oxygen consumption Signup and view all the answers

What can be a result of anaerobic metabolism in the fetus?

Hypoglycemia in the neonatal period Signup and view all the answers

What is one of the two possible consequences of CO2 accumulation in fetal circulation?

Reduced supply of O2 Signup and view all the answers

What changes occur in the blood composition of the umbilical vein during hypoxia?

Lower pO2, higher pCO2, and lower pH Signup and view all the answers

Which factor decreases the heart rate of the fetus?

Parasympathetic nerve (vagus) stimulation Signup and view all the answers

Study Notes

Physiology and Pathophysiology

This presentation covers fetal physiology and pathophysiology, including fetal circulation, fetal adaptations, baseline heart rate, variability, decelerations, and uterine contractions.
The fetus has a higher concentration of hemoglobin and a higher affinity for oxygen than an adult, enabling it to extract more oxygen from the placenta.
Fetal cardiac output is significantly higher than adult cardiac output.
Fetal physiology is designed to be oversupplied with oxygen.
The fetus is capable of accommodating significant reductions in oxygen supply through several adaptations.
Factors influencing fetal heart rate (FHR) include the nervous system, blood pressure, blood gas levels, cord compression, hypoxia, and cerebral activity.

Fetal Circulation

The placenta acts as a fetal lung, facilitating gas exchange between the mother and fetus.
Deoxygenated blood flows to the placenta via umbilical arteries.
The placenta facilitates gas exchange.
Oxygenated blood returns to the fetus via the umbilical vein.
Free gas exchange depends on normal maternal blood flow through the placental bed and normal blood flow through the placenta.

Fetal Adaptations

The fetus can adjust its circulation to prioritize critical organs (brain, heart, and adrenal glands) when faced with decreased oxygen supply.
The fetus can compensate for reduced oxygen supply by increasing oxygen extraction and centralizing blood flow.
Oxygen is crucial in aerobic metabolism of glucose to produce energy.
Damage to the heart or brain occurs with profound hypoxia, severe oxygen restriction.
Reduced maternal blood supply during labour is compensated for by fetal heart adaptation.

Baseline Heart Rate

Baseline heart rate is a proxy measure of cardiac output, reflecting the work of the heart.
Baseline heart rate is influenced by circulatory function for oxygen delivery and carbon dioxide removal.
Increased baseline rate indicates increased circulation.

Variability

Variability refers to short-term fluctuations in baseline heart rate.
Normal heart rate variability indicates good neurological function and fetal wellbeing.
Reduced variability may be a sign of fetal distress, such as from hypoxaemia or inadequate oxygen supply.
Reduced variability can result from hypoxaemia and chronic hypoxaemia.

Decelerations

Decelerations are transient falls in fetal heart rate.
They can be caused by various factors, such as head compression, cord compression, and reduced oxygen supply.
Decelerations are crucial for evaluating fetal physiological state, often associated with reduced oxygen delivery.
Early decelerations, variable decelerations, and late decelerations are different types of decelerations.
Decelerations are 'lost heart beats'.

Uterine Contractions

Uterine contractions are essential for labour progression.
They temporarily interrupt blood flow across the placenta, reducing oxygen supply to the fetus.
Carbon dioxide elimination from the fetus is also temporarily reduced.
Fetal recovery of oxygen and carbon dioxide exchange is essential between contractions, particularly during strong contractions.

Sinusoidal Patterns

A sinusoidal pattern in fetal heart rate implies severe fetal compromise, possibly from chronic hypoxaemia and/or hypoxia.
This pattern indicates significant, ongoing oxygen deprivation.
The inability of the fetus’ central nervous system to maintain adequate heart rate implies poor fetal well-being.

Summary

The presented material highlights fetal physiology, adapting to labour.
Normal physiology, adaptation, baseline rate, variability, decelerations, and abnormal patterns are critical points.

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Description

This quiz covers key concepts in fetal physiology and pathophysiology, focusing on fetal circulation, adaptations, and factors affecting fetal heart rate. Understanding these principles is crucial for comprehending how the fetus interacts with its environment, especially regarding oxygen supply and cardiac function. Test your knowledge on these critical aspects of fetal development and health.