It has been used for decades during labor to detect abnormal fetal heart rate patterns. (sciencedaily.com)
When the baby's heart rate pattern demonstrates a lack of oxygen (fetal distress) it is necessary for the baby to be born immediately. (birthingnaturally.net)
Of note to anesthesiologists, the ACOG Committee Opinion No. 197 states that «performing a cesarean delivery for a nonreassuring fetal heart rate pattern does not necessarily preclude the use of regional anesthesia.» (birthingnaturally.net)