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Abstract

We thank Drs Illuzzi and Bracken for their letter to the editor regarding our article which ascertained the association between the use of electronic fetal monitoring (EFM) and risk of adverse infant morbidity and mortality.1Chen H.-Y. Chauhan S.P. Ananth C.V. Vintzileos A.M. Abuhamad A.Z. Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States.Am J Obstet Gynecol. 2011; 204: 491.e1-491.e10Abstract Full Text Full Text PDF Scopus (94) Google Scholar We concur that one of the strengths of our investigation is the large sample size but there are other strengths as well. The first is the consistency of our findings with those previously reported, and subsequently corroborated by a large metaanalysis with respect to operative deliveries and perinatal mortality.2Alfirevic Z. Devane D. Gyte G.M. Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.Cochrane Database Syst Rev. 2006; 3 (CD006066)PubMed Google Scholar The second is the number needed to treat (NNT) to avert 1 neonatal death in our analysis is similar to prior publications.3Vintzileos A.M. Nochimson D.J. Guzman E.R. Knuppel R.A. Lake M. Schifrin B.S. Intrapartum electronic fetal heart rate monitoring versus intermittent auscultation: a meta-analysis.Obstet Gynecol. 1995; 85: 149-155Crossref PubMed Scopus (183) Google Scholar The third is the biologic plausibility of our findings. Although we concur with Drs Illuzzi and Bracken's concern that women who were not electronically monitored may be heterogeneous, so may be those who had EFM. We disagree with their notion that the non-EFM group was at increased baseline risk because of the need for emergent cesarean delivery caused by vaginal bleeding, abdominal trauma, footling breech, or poor biophysical profile. In clinical practice, in all the aforementioned situations, EFM use is necessary to determine the urgency for delivery. As a matter of fact, EFM (in the form of nonstress test) is an integral part of the traditional biophysical profile.4Manning F.A. Baskett T.F. Morrison I. Lange I. Fetal biophysical profile scoring: a prospective study in 1,184 high-risk patients.Am J Obstet Gynecol. 1981; 140: 289-294Abstract Full Text PDF PubMed Scopus (162) Google Scholar Thus, the assumption by Drs Illuzzi and Bracken that patients with all the above conditions were included in the non-EFM group has no basis. With respect to the NNT to prevent 1 early neonatal death according to risk status, we reanalyzed our data and we found that the NNT to prevent 1 early neonatal death in low-risk pregnancies is 9508, whereas the corresponding NNT for high-risk pregnancies is 251. This observation, coupled with our earlier finding that there was a dose-response relationship between gestational age and NNT (with lower NNT in early gestations), suggests that the association of EFM use and decreased neonatal and infant mortality may indeed be causal. We disagree with the notion that the randomized trials (and therefore their metaanalysis) “compared EFM with properly performed intermittent auscultation (IA).”2Alfirevic Z. Devane D. Gyte G.M. Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour.Cochrane Database Syst Rev. 2006; 3 (CD006066)PubMed Google Scholar With the exception of the Athens trial5Vintzileos A.M. Antsaklis A. Varvarigos I. Papas C. Sofatzis I. Montgomery J.T. A randomized trial of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation.Obstet Gynecol. 1993; 81: 899-907PubMed Google Scholar none of the other trials was a direct comparison of EFM vs IA as the primary and only method of intrapartum fetal surveillance. The remaining trials were comparisons of policies or protocols allowing for cross-over from IA to EFM (when there were fetal heart rate abnormalities by auscultation) and back-up methods, such as scalp pH, which apparently can mask any clinical outcome differences that exist between the 2 monitoring techniques. In conclusion, despite Drs Illuzzi and Bracken's concern, we reiterate our earlier conclusions that “In the United States, the use of EFM was associated with a substantial decrease in early neonatal mortality and morbidity.1Chen H.-Y. Chauhan S.P. Ananth C.V. Vintzileos A.M. Abuhamad A.Z. Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States.Am J Obstet Gynecol. 2011; 204: 491.e1-491.e10Abstract Full Text Full Text PDF Scopus (94) Google Scholar” We look forward to a large and adequately powered randomized, controlled trial to disprove our conclusions. Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United StatesAmerican Journal of Obstetrics & GynecologyVol. 206Issue 2PreviewChen et al1 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,2 but on closer examination many of its findings may be substantially biased. Full-Text PDF