Electronic fetal monitoring (EFM) is a common form of monitoring of your baby and contractions during your labor and birth. External fetal monitoring uses two belts: one that uses ultrasound to measure your baby's heart rate and the other is a pressure transducer used to measure your contractions. This prints out onto paper or a computer screen a graphical representation of your baby's heart rate in response to your contractions.
In a low risk patient this type of monitoring should be done for about 15-20 minutes out of every hour during the first stage of labor and five minutes out of 15 minutes in the second stage or pushing phase of labor.
If you are having complications and require medications like epidural anesthesia, pitocin, other medications or if your baby is having a hard time tolerating labor, it may be a reason to do more fetal monitoring.
Since external fetal monitoring uses ultrasound and pressure to get its readings, they may not be as accurate as other forms of monitoring.
Electronic fetal monitoring has its risks too. It has not been shown to decrease the infant mortality rates as it was initially purported to do. It does increase the intervention rates like cesarean section. It has also been linked to making labor more painful because of the lack of movement when being monitored. Be sure to talk to your doctor or midwife about moving around while being monitored or using alternative forms of monitoring like auscultation, Dopplers, etc.
More Information: Other Interventions in Labor