Which method is used to continuously monitor uterine contractions during labor?

The external tocodynamometer is the correct choice for continuously monitoring uterine contractions during labor. This device is placed on the mother's abdomen and uses sensors to detect the pressure changes caused by uterine contractions. It provides ongoing real-time data about the frequency, duration, and intensity of contractions, which is crucial for assessing labor progress and ensuring the safety of both the mother and the fetus.

While manual palpation can provide some information about uterine contractions, it is not continuous or as precise as the readings from a tocodynamometer. A fetal electrocardiogram is used primarily to monitor the fetal heart rate, not uterine contractions. Lastly, a vaginal examination can give insights into cervical dilation and effacement but does not provide information regarding the contraction pattern over time. Thus, the external tocodynamometer stands out as the most effective method for continuous monitoring of uterine contractions during labor.