Cardiotocography (CTG) involves using ultrasound and pressure transducers on a pregnant woman's abdomen to monitor the fetal heart rate and uterine contractions. It is used in the third trimester, especially during labor, to detect fetal distress. Abnormal CTG readings may indicate the need for further investigation or emergency c-section. Key elements of CTG interpretation include assessing the baseline fetal heart rate, variability, accelerations, and decelerations in response to contractions. Late or variable decelerations can suggest fetal hypoxia requiring interventions like fetal blood sampling.