Image 1: M mode above showing fetal heart rate of 148 beats per minute. This is correct, adheres to ALARA principle.
Image 2: Doppler above showing fetal heart rate of 148 beats per minute. This is incorrect, does not adhere to ALARA principle.
As Low As Reasonably Achievable (ALARA) when applied to fetal heart rate assessment can be boiled down to the message; use M mode (Image 1), never doppler (Image 2). The potential deleterious effects of heat from doppler brackets concentrated on the fetal heart (Image 2) can be avoided by m-mode (Image 1), so it should be.
POCUS Pearl: When assessing fetal heart rate in the emergency department please never use doppler, doing so goes against the ALARA principle.