When monitoring a newborn's heart rate, if it cannot be determined with a stethoscope, what should be done next?

When monitoring a newborn's heart rate, if it cannot be determined with a stethoscope, using an ECG (electrocardiogram) and/or a pulse oximeter is the appropriate next step. This is crucial because accurate heart rate monitoring is essential in assessing the newborn's condition, particularly in situations that may demand immediate resuscitation or intervention.

An ECG provides a direct measurement of the electrical activity of the heart, allowing healthcare providers to determine heart rate quickly and reliably, especially when the stethoscope is ineffective. A pulse oximeter can also provide indirect information about the heart rate by measuring the oxygen saturation of the blood and can often display the heart rate simultaneously.

In contrast, a digital thermometer does not measure heart rate and is not relevant in this context. A chest X-ray is unnecessary and impractical for immediate heart rate assessment. Continuing to check with the stethoscope would delay critical care if the heart rate is not being obtained, which could be detrimental in an emergency situation. Thus, utilizing ECG and/or pulse oximetry is the most effective and accurate approach in this circumstance.