A method and device for monitoring a fetal heart rate includes a reference fetal heart rate detected across an ultrasound depth zone of sensitivity. The ultrasound depth zone of sensitivity is scanned in overlapping increments of a first depth. An average fetal heart rate detected for each overlapping increment is tested for a coincidence with the reference fetal heart rate. Overlapping increments with the coincidence and a maximized signal quality rate are identified. An ultrasound depth increment of a second depth is selected representing the selected adjacent increments. Fetal heart rate is determined from an ultrasound signal returned from a scan depth of the second depth.
