Assessment of the fetus during labor is a challenging task. The rationale for monitoring the fetal heart rate (FHR) is that FHR patterns are indirect markers of the fetal cardiac and medullary responses to blood volume changes, acidemia, and hypoxemia, since the brain modulates heart rate. Virtually all obstetrical organizations advise monitoring the FHR during labor. This position is largely based upon the experience of experts and medicolegal precedent; no trials comparing electronic fetal monitoring versus no monitoring have been performed . A trial comparing auscultation with no monitoring found that auscultation was associated with an increased risk of operative delivery without any reduction in perinatal mortality . Furthermore, no reliable auscultatory indicator of fetal distress has been determined, other than extreme changes in FHR . Thus, neither electronic fetal monitoring nor auscultation has been proven to reduce mortality, despite large clinical trials .
Intrapartum fetal monitoring will be discussed here. Fetal cardiac physiology, FHR patterns, and antepartum FHR monitoring (nonstress test, contraction stress test) are reviewed separately. (See "Antepartum fetal heart rate assessment".)
EFFECTIVENESS OF INTRAPARTUM FHR MONITORING
The primary goal of FHR monitoring is to identify hypoxemic and acidotic fetuses in whom timely intervention will prevent death. A secondary goal is to avoid fetal neurologic injury, if possible. The two commonly used modalities for intrapartum FHR monitoring, continuous electronic FHR monitoring and intermittent auscultation, have been extensively reviewed; there is no high quality evidence that these techniques achieve either of these goals or that one performs better than the other in low risk pregnancies [4-10]. In early studies of intermittent auscultation versus no monitoring, FHR monitoring was not associated with a decrease in perinatal mortality or neurological disability despite an increased incidence of operative delivery [2,3].
A 2013 systematic review of 13 randomized trials (two of high quality) including >37,000 women (both low and high risk) that compared continuous electronic FHR monitoring to intermittent auscultation found no significant difference between techniques in :
●Perinatal mortality (RR 0.86, 95% CI 0.59-1.24)