Chen et al found decreased early neonatal mortality rates among infants who were recorded on birth certificates as having had electronic fetal monitoring (EFM) during labor compared with those who did not have EFM recorded on the birth certificate. The authors invoke the large size of this study as a major strength over RCTs comparing EFM and intermittent auscultation (IA). At first glance, this observational study would seem to affirm widely supported, validated recommendations to monitor the fetal heart rate during labor, but on closer examination many of its findings may be substantially biased.

In this study, the non-EFM group is clinically heterogeneous, including precipitous deliveries, births where EFM was not available even if indicated, and unplanned out of hospital births. Likewise, any women taken immediately for cesarean delivery because of severe vaginal bleeding, abdominal trauma, poor biophysical profile, footling breech, or cord prolapse would be unlikely to have had intrapartum EFM. All of these deliveries are at increased risk for adverse outcome and appear to be included in the non-EFM group.

Inexplicably, the authors stratify by high- and low-risk pregnancy for some neonatal morbidity outcomes, but not for neonatal mortality, the primary outcome of interest. The calculated number needed to treat (NNT) to prevent 1 early neonatal death at ≥37 weeks is 10,949. However, the NNT for the majority of the pregnant population—low-risk, term pregnancies with adequate opportunity for EFM or IA, in which rates of neonatal death are low—would likely be substantially higher.

Although interesting to know if EFM recorded on the birth certificate is associated with expected outcomes in the “real world” compared with no EFM, such an approach does not estimate the incremental benefit of EFM compared with IA with sufficient accuracy to inform policy and practice. Metaanalyses of randomized trials include fewer patients, but avoid bias and compare EFM with properly performed IA (which, if necessary, should be converted to EFM, followed by timely intervention). Larger, well-designed observational studies comparing EFM with IA in practice would be informative.

The non-EFM comparison group in the current study included women with no opportunity for fetal heart monitoring and potential for the worst outcomes. Therefore, this study would appear quite limited in its ability to shed light on the actual benefits or risks attributable to EFM itself, especially in comparison to IA, which in this study comprised an unknown proportion of the comparison group.