Zhango), Landy H), Branch OW, et al: Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 116: 1281, 2010 Zhang], Troendle ]F, Yancey MK: Reassessing the labor curve in nulliparous women. m) Obstet GynecoIo187(4):824, 2002
ELECTRONIC FETAL MONITORING ................. 457
OTHER INTRAPARTUM ASSESSMENT TECHNIQUES ... 470
NONREASSURING FETAL STATUS ................. 472
MECONIUM IN THE AMNIONIC FLUID .............. 474
FETAL HEART RATE PAIERNS AND BRAIN INJURY ... 476
CURRENT RECOMMENDATIONS ................... 478
INTRAPARTUM SURVEILLANCE OF UTERINE ACTIVIY ... 478
To study the orces exerted by labour, a rubber bag was inserted into the uterus which was connected with a manometer. In this way it was ound that the intra-uterine pressure, in the intervals between the contractions, was represented by a column of mercury 20 millimeters high, 5 of which were due to the toniciy of the wals and 15 to its contents. During the pains, however, the mercury rose consideraby, reaching a height of from 80 to 250 milimeters.
-J. Whitridge Williams (1903)
Little is written in the first edition of this textbook concerning monitoring of the fetus during labor. Much later, periodic auscultation of the fetal heartbeat with a fetoscope was adopted. These practices were eclipsed in the late 1960s and early 1970s by the development of electronic fetal monitoring (Hon, 1958). It was hoped that the continuous graph-paper portrayal of the fetal heart rate was potentially diagnostic in assessing pathophysiological events afecting the fetus.
When first introduced, electronic fetal heart rate monitoring was used primarily in complicated pregnancies but gradually became used in most pregnancies. Now, more than 85 percent of all live births in the United States undergo electronic fetal monitoring (Ananth, 2013).
Direct fetal heart measurement is accomplished by attaching a bipolar spiral electrode directly to the fetus (Fig.
The wire electrode penetrates the fetal scalp, and the second pole is a metal wing on the electrode. The electrical fetal cardiac signal-P wave, QRS complex, and T wave-is ampliied and must be applied because air conducts ultrasound waves poorly. he device Mother 50 mm/sec
FIGURE 24-1 Internal electronic fetal monitoring. Schematic representation of a bipolar electrode attached to the fetal scalp for detection of fetal QRS complexes (F). Also shown is the maternal heart and corresponding electrical complex (M) that is detected.
is held in position by an elastic belt.
FIGURE 24-3 The top tracing shows standard fetal monitor tracing of heart rate using a fetal scalp electrode, Spiking ofthe fetal rate in the monitor tracing is due to premature atrial con entiation of fetal cardiac motion from tractions, The second panel displays accompanying contractions, The bottom two tracings repmaternal arterial pulsations (Neilson, resent cardiac electrical complexes detected from fetal scalp and maternal chest wall electrodes, 2008). ECG = electrocardiogram; F = fetus; M = mother; PAC = fetal premature atrial contraction, fed into a cardiotachometer for heart rate calculation. he peak R-wave voltage is the portion of the fetal electrocardiogram (ECG) most reliably detected.