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The use of intrapartum EFM seems to increase the number of cesarean and operative vaginal deliveries.
This hope was based on retrospective studies comparing EFM to historic controls, studies in which auscultation was performed in a nonstandardized manner. Over the past three decades, EFM has been subjected to more rigorous evaluation; in fact more than 12 randomized clinical trials involving nearly 40,000 laboring women have been carried out to investigate its safety and efficacy.1,2 These studies suggest that, when compared with standardized intermittent auscultation, the use of intrapartum EFM seems to increase the number of cesarean and operative vaginal deliveries but has no significant effect on the incidence of intrapartum death or long-term neurologic injury.1,2
The benefits of EFM
Although intrapartum EFM may or may not be better than careful intrapartum auscultation in improving long-term perinatal outcome, the reality is that meticulous intermittent auscultation requires intensive labor and delivery nursing resources that are currently impracticable and, with the growing shortage of such nurses across the country, may soon be impossible. It is also clear that EFM has not reduced the occurrence of cerebral palsy. It is true that the rate of CP in the United States, currently estimated at 2.8 per 1,000 children aged 3 to 10,3 has not significantly decreased over the past three decades, despite the widespread use of intrapartum EFM and a five- to sixfold increase in the cesarean delivery (CD) rate. However, during this same time period there has been a dramatic increase in the survival of premature neurologically impaired infants, which has masked a reduction in CP among term infants due to intrapartum EFM-associated reductions in intrapartum asphyxia.4,5 For these and more complex medicolegal reasons, in my opinion intrapartum EFM will not be abandoned anytime soon. Instead, investigators have focused on the development of complementary technologies to better refine the interpretation of intrapartum EFM to reduce the frequent false-positive and occasional false-negative results.
What role should fetal pulse oximetry play?
In May 2000, the FDA granted conditional approval to the OxiFirst Fetal Oxygen Saturation Monitoring System (Mallinckrodt/Nellcor, Pleasanton, Calif.), as an adjunct to intrapartum EFM. Using an oxygen sensor placed against the fetal face during labor, this device theoretically provides a continuous measurement of fetal oxygen saturation throughout labor. The goal is to provide fetal oxygen saturation data in real time in laboring woman with nonreassuring fetal heart rate tracings so that the provider can more accurately assess fetal well-being and avoid an unnecessary CD.
An early study generated guarded optimism.6 Investigators randomized over 1,000 parturients with nonreassuring fetal testing to either intrapartum EFM plus fetal pulse oximetry or intrapartum EFM alone. They found a significant reduction in the rate of CD-from 10.2% to 4.5% (P=0.007)-for the group with nonreassuring EFM readings who were assigned to pulse oximetry. Unfortunately, there was no decrease in the overall CD rate because of an unexpected increase in CD for the indication of 'dystocia' in the oximetry group. Moreover, perinatal outcome was no different between the two groups.