Which method provides a direct measurement of fetal ECG?

The fetal spiral electrode is the correct choice because it provides a direct measurement of the fetal electrocardiogram (ECG) by being attached directly to the fetal scalp. This invasive method allows for continuous monitoring of the fetal heart rate and provides more accurate data regarding the fetal cardiac rhythm and any potential abnormalities. Since it is in direct contact with the fetal tissue, it can pick up the electrical signals from the fetal heart, which can be vital for assessing the well-being of the fetus during labor.

In contrast, external ultrasound methods, such as external fetal monitors, rely on ultrasound technology to assess fetal heart rate patterns but do not provide direct ECG readings. Similarly, a fetoscope is a handheld tool that allows listening to the fetal heart sounds but does not record electrical activity like an ECG does. Transabdominal ultrasound is used for imaging and can provide information about the fetus's position and behavior but, again, it does not measure fetal ECG directly. Therefore, the fetal spiral electrode stands out as the method that delivers precise and direct data related to fetal cardiac activity.