Fetal Heart Rate Monitoring Quiz

Physiology and Pathophysiology

• This presentation covers fetal physiology, specifically fetal circulation, metabolism, and gas exchange.
• It also discusses common issues like fetal heart rate (FHR) variations, uterine contractions, and decelerations.
• The content includes the role of the placenta in fetal gas exchange, fetal metabolism (aerobic and anaerobic), and the regulation of fetal heart rate.
• It reviews various types of decelerations, including early, variable, and late decelerations, and the clinical significance of these variations.
• The lecture explores factors affecting FHR, such as cord compression, hypoxia, maternal blood pressure, and uterine contractions.
• It examines the relationship between the fetal heart rate and various conditions and factors, including FHR variability, fetal oxygen supply, and uterine contractions.
• Normal FHR variability and the factors that reduce it are also examined.

Fetal Circulation

• The fetus pumps deoxygenated blood to the placenta via two umbilical arteries.
• The placenta acts as a fetal lung, facilitating gas exchange between the mother and fetus.
• Maternal blood flows through the placental bed, enabling gas exchange and essential nutrient transfer to the fetal blood.
• Blood is pumped back to the fetus via the single umbilical vein.

Fetal Metabolism

• The fetus utilizes oxygen in glucose metabolism to produce energy through aerobic metabolism.
• Carbon dioxide (CO2) is a waste product of this metabolism.
• Some CO2 is carried in solution, while most is buffered by haemoglobin (Hb) forming bicarbonate (HCO3).
• The elimination of CO2 from the fetus to the mother through the placenta is crucial for maintaining normal pH.
• In cases of insufficient oxygen, the fetus may switch to anaerobic metabolism, resulting in lactic acid accumulation and potentially acid-base imbalances— metabolic acidosis.

Fetal Heart Rate (FHR)

• Baseline heart rate reflects cardiac output over a period and can be a proxy for the efficiency of blood circulation.
• Higher baseline heart rates suggest increased circulation.
• Baseline heart rate may increase due to compensatory increases in circulation to maintain oxygen supply when oxygen levels drop (hypoxia).
• A drop in baseline heart rate may, in some cases, be due to insufficient energy supplying the heart or excessive parasympathetic nerve stimulation, often as a result of head compression in the birth canal.

Uterine Contractions

• Uterine contractions are crucial for labor progression.
• During contractions, blood flow to the placenta is temporarily reduced, affecting oxygen and carbon dioxide exchange with the fetus.
• The intervals between contractions allow the fetus to recover.
• Prolonged or abnormally strong contractions can impede circulatory or respiratory homeostasis.

Decelerations

• Decelerations are temporary reduced heart rate.
• They are a common finding during labor.
• Various factors could cause decelerations like: baroreceptors, chemoreceptors, vagal nerve stimulation etc.
• Early, variable, and late decelerations have different characteristics and potential implications for fetal well-being.
• Long-term decelerations may indicate serious fetal compromise.

Sinusoidal Patterns

• Sinusoidal fetal heart rate patterns are consistently rhythmic, suggesting profound and continuing fetal compromise
• Linked with chronic hypoxaemia and often an indication of serious fetal distress requiring urgent intervention.

Additional Reading

• Various resources are available on fetal heart rate monitoring and other relevant topics in maternal-fetal care.
• Several guidelines and consensus papers on fetal monitoring are suggested for further study.

This quiz tests your knowledge on fetal heart rate patterns during labor, including decelerations and their physiological implications. Explore the differences between early, variable, and prolonged decelerations, and their relationship to fetal hypoxemia. Understand the conditions that affect fetal heart rate responses.