EFM (electronic fetal monitoring) uses ultrasound waves to hear your baby’s heart. Your midwife uses a machine called a transducer, held against your abdomen or a small electrode clipped onto your baby’s scalp or bottom if your baby's breech.
EFM monitors your baby continuously. For some babies this can be very important - if they are at risk or if it's known that there may be an issue.
However:
In many hospitals midwives agree that continuous EFM is not needed for normal labour, especially in the first stage.
Sometimes a Doppler or Pinard stethoscope is used instead.