Introduction to CTG Interpretation cardiotocography (CTG) is a crucial tool in obstetrics, enabling healthcare professionals to monitor fetal well-being during pregnancy and labor. Understanding how to interpret CTG results is vital for ensuring the safety and health of both the mother and the fetus. This guide will cover everything you need to know about CTG interpretation, from the basics to more advanced techniques, offering practical insights for doctors and healthcare professionals. 1. The Basics of CTG: What You Need to Know CTG involves the continuous monitoring of the fetal heart rate (FHR) and uterine contractions. The FHR is plotted on a graph, with time on the x-axis and heart rate on the y-axis. Uterine contractions are also recorded simultaneously on the graph. 1.1 Components of CTG Baseline FHR: The average heart rate of the fetus between contractions, typically ranging between 110-160 bpm. Variability: The fluctuations in FHR, reflecting the fetal autonomic nervous system's response. Normal variability is between 5-25 bpm. Accelerations: Transient increases in FHR, often associated with fetal movements. Accelerations are usually a sign of fetal well-being. Decelerations: Transient decreases in FHR, which may indicate fetal distress, especially if repetitive and severe. Uterine Contractions: Recorded as the frequency, duration, and intensity of contractions, typically measured in millimeters of mercury (mmHg). 1.2 Understanding the CTG Paper The CTG paper runs at a standard speed of 1 cm per minute, with each small square representing 10 seconds. Familiarity with the scale is crucial for accurate interpretation. 2. Step-by-Step Guide to CTG Interpretation 2.1 Step 1: Assess the Baseline FHR The baseline FHR should be evaluated over a minimum of 10 minutes. A normal baseline FHR is between 110-160 bpm. A baseline FHR below 110 bpm is classified as bradycardia, while above 160 bpm is tachycardia. Both conditions require careful monitoring and possible intervention. 2.2 Step 2: Evaluate Variability FHR variability is one of the most critical indicators of fetal well-being. Reduced variability (<5 bpm) can be a sign of fetal hypoxia or other complications. Variability should be evaluated over a 10-minute period, excluding periods of accelerations and decelerations. 2.3 Step 3: Identify Accelerations Accelerations are temporary increases in FHR, typically by at least 15 bpm for at least 15 seconds. The presence of accelerations is generally reassuring, indicating an active, well-oxygenated fetus. 2.4 Step 4: Identify Decelerations Decelerations are classified into four types: Early Decelerations: These mirror uterine contractions and are usually benign, related to fetal head compression during labor. Late Decelerations: These begin after the peak of the contraction and are associated with uteroplacental insufficiency, which can indicate fetal distress. Variable Decelerations: These are abrupt and can vary in duration and intensity, often associated with umbilical cord compression. Prolonged Decelerations: Lasting more than 2 minutes but less than 10 minutes, prolonged decelerations can indicate a significant problem, requiring immediate attention. 2.5 Step 5: Assess Uterine Activity Evaluate the frequency, duration, and intensity of uterine contractions. Excessive uterine activity (tachysystole) can lead to fetal distress and should be managed promptly. 2.6 Step 6: Overall Interpretation Based on the findings from the above steps, CTG can be categorized as: Normal: No concerning features; continue routine monitoring. Suspicious: Some abnormal features; requires closer monitoring and possible intervention. Pathological: Abnormal features present; immediate action required, possibly including delivery. 3. Common CTG Patterns and Their Implications 3.1 Sinusoidal Pattern A sinusoidal pattern is a smooth, sine wave-like pattern in FHR, typically indicating severe fetal anemia or hypoxia. This pattern requires immediate intervention. 3.2 Pseudosinusoidal Pattern This pattern may resemble a sinusoidal pattern but is usually benign and can be associated with maternal opiate use. Differentiating between the two is crucial for appropriate management. 3.3 Tachysystole Defined as more than five contractions in 10 minutes, tachysystole can reduce uteroplacental blood flow and lead to fetal hypoxia. Management may include reducing or stopping oxytocin if being administered. 3.4 Bradycardia Bradycardia, defined as an FHR below 110 bpm for more than 10 minutes, may indicate severe fetal distress, requiring immediate intervention, such as intrauterine resuscitation or delivery. 4. Advanced Techniques in CTG Interpretation 4.1 ST Segment Analysis (STAN) STAN involves monitoring the ST segment of the fetal ECG, providing additional information on fetal hypoxia. It is used alongside traditional CTG, particularly in high-risk cases. 4.2 Fetal Scalp Sampling If the CTG is suspicious or pathological, fetal scalp blood sampling can assess the pH or lactate levels, offering more direct insight into fetal oxygenation. 4.3 Computerized CTG Analysis Computerized systems can assist in CTG interpretation by providing objective analysis of FHR patterns, reducing inter-observer variability. 5. Clinical Scenarios and Case Studies 5.1 Case Study 1: Persistent Late Decelerations A 32-year-old woman at 40 weeks gestation presents with persistent late decelerations on CTG. Despite intrauterine resuscitation, decelerations persist, and the decision is made for an emergency cesarean section. The baby is delivered safely, highlighting the importance of timely intervention. 5.2 Case Study 2: Variable Decelerations with Tachysystole A 28-year-old woman at 38 weeks gestation presents with variable decelerations and tachysystole after oxytocin augmentation. The oxytocin is stopped, and decelerations resolve, demonstrating the need for careful management of uterine activity. 5.3 Case Study 3: Sinusoidal Pattern A 25-year-old woman at 36 weeks gestation presents with a sinusoidal CTG pattern. Fetal anemia is suspected, and intrauterine transfusion is performed, stabilizing the fetal condition. 6. Practical Tips for Accurate CTG Interpretation 6.1 Consistent Monitoring Continuous monitoring is crucial for detecting changes in FHR patterns that may indicate fetal distress. 6.2 Collaborate with Colleagues Consultation with colleagues and second opinions can be invaluable, particularly in complex cases. 6.3 Stay Updated CTG interpretation guidelines evolve; staying current with the latest recommendations is essential. 6.4 Patient Communication Effective communication with the patient is crucial, explaining the findings and the rationale for any interventions. 7. Conclusion CTG interpretation is a critical skill in obstetrics, requiring a thorough understanding of fetal physiology and the ability to recognize abnormal patterns. This guide provides a comprehensive overview of CTG interpretation, offering practical insights and case studies to help healthcare professionals improve their skills and ensure the best outcomes for their patients.
