- Email: [email protected]
Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States
Letters to the Editors ity as opposed to high specificity as we did not want women with bleeding disorders to be missed for further testing at the initial stage of evaluation. A sequential approach with an initial highly sensitive screen is a common approach3 and takes into account the fundamental differences between screening and diagnostic testing.4 We believe that the likelihood ratio should be applied for the posttest probability of a clinical diagnosis of a bleeding disorder after diagnostic laboratory testing and a comprehensive bleeding history is performed. We believe the screening tool has potential use as an initial screen in gynecology practice to improve hematology referral of a large multif racial menorrhagia population. Claire S. Philipp, MD Ambarina Faiz, MD, PhD MEB Rm 378 Division of Hematology
www.AJOG.org UMDNJ-Robert Wood Johnson Medical School New Brunswick, NJ 08903 [email protected] The authors report no conflict of interest.
REFERENCES 1. Philipp CS, Faiz A, Heit JA, et al. Evaluaton of a screening tool for bleeding disorders in a US multisite cohort of women with menorrhagia. Am J Obstet Gynecol 2011;204:209.e1-7. 2. Kirtava A, Crudder S, Dilley A, Lally C, Evatt B. Trends in clinical management of women with von Willebrand Disease: a survey of 75 women enrolled in haemophilia treatment centres in the United States. Hemophilia 2004;10:158-61. 3. Grimes DA, Schulz KF. Uses and abuses of screening tests. Lancet 2002;359:881-4. 4. Evans MI, Galen RS, Britt DW. Principles of screening. Semin Perinatol 2005;29:364-6. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2011.07.005
Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States TO THE EDITORS: The Journal recently published an article suggesting a causal association between electronic fetal monitoring (EFM) and decreased infant mortality.1 We have strong reservations regarding the ability of that paper to offer guidance regarding the effectiveness of EFM because it is inappropriate to use vital statistics data to make the leap from statistical association to causation. Several years ago, two of us contributed to a set of American Journal of Obstetrics and Gynecology commentaries discussing the reasonable use of secondary vital statistics data.2,3 Those commentaries raised important issues and limitations that should be considered, acknowledged, and addressed. The first issue is the potential inaccuracy of the EFM data. Validation of birth certificates has found that obstetric procedures, including EFM, are particularly poorly reported.4 Although random underreporting of EFM would bias estimates of the association between EFM and mortality toward finding no difference, it may be optimistic to assume that underreporting is random. We are aware of no study evaluating differential reporting of obstetric procedures, but it is plausible that reporting of intrapartum events may be less complete when, for example, an ill neonate is transferred shortly after birth.3 Differential reporting could bias the relative risk in either direction. The second issue is confounding. Even if EFM were perfectly reported, we doubt that the factors controlled for by Chen et al,1 maternal age, race/ethnicity, education, marital status, self-reported tobacco and alcohol use, and infant sex, are the most relevant characteristics to explain how the 11% of labors that were not monitored differed from the 89% that were. Of great concern is the inability to ascertain the clinical circumstances of the labors. Among the many unmeasured potentially confounding factors are precipitous delivery or delivery in settings without easy access e18
American Journal of Obstetrics & Gynecology JANUARY 2012
to EFM (and, perhaps, specialized obstetric care). These factors would be associated with both lack of EFM and adverse outcome. Lastly, there is inappropriate use of causal language and inference in the description and interpretation of these crosssectional administrative data. Within the limitations of birth certificate data, the paper by Chen et al1 may provide a helpful description of EFM use. However, it should not be used as a basis for clinical decision making, nor should the association between EFM and decreased infant mortality be deemed a causal one on the basis of this analysis. f Mark A. Klebanoff, MD, MPH Director Ohio Perinatal Research Network Department of Pediatrics The Ohio State University College of Medicine and Nationwide Children’s Hospital Columbus, OH 43205 [email protected] Amy M. Branum, PhD, MSPH Kenneth C. Schoendorf, MD, MPH Infant, Child, and Women’s Health Statistics Branch National Center for Health Statistics Centers for Disease Control and Prevention Hyattsville, MD 20782 Courtney D. Lynch, PhD, MPH Director of Reproductive Epidemiology Department of Obstetrics and Gynecology The Ohio State University College of Medicine Columbus, OH 43210 The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Center for Health Statistics, Centers for Disease Control and Prevention.
Letters to the Editors
www.AJOG.org REFERENCES 1. Chen HY, Chauhan SP, Ananth CV, Vintzileos AM, Abuhamad AZ. Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States. Am J Obstet Gynecol 2011;204: 491.e1-10. 2. Cahill AG, Macones GA. Vital considerations for the use of vital statistics in obstetrical research. Am J Obstet Gynecol 2006;194:909-10. 3. Schoendorf KC, Branum AM. The use of United States vital statistics in perinatal and obstetric research. Am J Obstet Gynecol 2006;194:911-5. 4. Dobie SA, Baldwin LM, Rosenblatt RA, Fordyce MA, Andrilla CHA, Hart LG. How well do birth certificates describe the pregnancies they report? The Washington State experience with low-risk pregnancies. Matern Child Health J 1998;2:145-54. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2011.08.008
REPLY We are delighted that our article1 exploring the association between the utilization of electronic fetal monitoring (EFM) and risk of adverse infant morbidity and mortality has evinced interest from Klebanoff et al.2 At the outset, we were surprised to note that Klebanoff et al2 have expressed concerns regarding an evaluation of the benefits of EFM based on vital statistics data when they themselves, since 1992, have collectively published at least 36 articles that are based on the vital statistics data. This irony aside, let us address the primary concerns about our publication.1 First, Klebanoff et al2 worry that we inappropriately used the vital statistics data “to make the leap from statistical association to causation.” We do not. May we point out that the very first sentence of the abstract states the objective was “to examine the association between EFM and neonatal and infant mortality as well as neonatal morbidity?” In the study design portion of the abstract, we wrote the “estimate risk ratio for association between electronic fetal heart rate monitoring and mortality.” In the introduction, we noted that “the primary objective of this study was to examine the association between EFM during labor and corrected neonatal and infant mortality in the United States.” Although it is possible to draw causal inferences, our goal was to infer only associations in the article. However, it should be also noted that we found a significant dose-response relationship between gestational age and the number needed to treat with earlier gestations requiring the least number needed to treat. Second, Klebanoff et al2 argue about the “potential inaccuracy of the EFM data.” Under the section of strengths and weakness section of our article,1 the very first limitation we acknowledged was that “studies based on birth certificates have been criticized because of the quality of the data.” Nonetheless, it is noteworthy that our finding of significant increased rate of operative deliveries for fetal distress3 and decrease in neonatal seizures associated with EFM utilization is consistent with a metaanalysis of 12 randomized controlled trials (RCTs) on EFM.4 We do acknowledge that some degree of misclassification of EFM on vital statistics data is likely, but we wonder whether it really is possible that limitations of vital statistics
provide results concordant with RCTs when focused on morbidity and not on mortality. Third, Klebanoff et al2 are apprehensive about the role of unmeasured confounders on our findings. Although we did not specifically draw attention to the role of unmeasured confounders on the associations that we reported, it is very unlikely that a complete adjustment for “all possible confounders” would drive the strong associations of EFM use and early neonatal deaths and a low 5 minute Apgar score that we report toward the null. In addition, we underscore the congruity of our findings and that of earlier publications, including a metaanalysis of 12 RCTs.4 After careful reading of their concerns, we affirm that our data indicate what we concluded before: “In the United States, the use of EFM was associated with a substantial decrease in early neonatal mortality and morbidity.” We do welcome large and adequately powered RCTs to disprove our conclusions; like Freeman and Nageotte,5 we do not subscribe to the nihilistic view of the EFM and believe that the best evidence of the benefits of EFM may not come from the small RCTs but from f the largest observational study reported to date.1 Suneet P. Chauhan, MD Director, Maternal-Fetal Medicine Department of Obstetrics-Gynecology Eastern Virginia Medical School 825 Fairfax Ave. Norfolk, VA 23507 [email protected] Han-Yang Chen, MS Biostatistician Assistant Researcher Center for Urban Population Health University of Wisconsin School of Medicine and Public Health Milwaukee, WI 53233 Cande V. Ananth, PhD, MPH Professor of Reproductive Sciences Department of Obstetrics and Gynecology Columbia University Medical Center New York, NY 10032 Anthony M. Vintzileos, MD Chairman and Program Director Department of Obstetrics and Gynecology Winthrop University Hospital Mineola, NY 11501 Alfred Z. Abuhamad, MD Chairman Department of Obstetrics and Gynecology Eastern Virginia Medical School 825 Fairfax Ave. Norfolk, VA 23507 REFERENCES 1. Chen HY, Chauhan SP, Ananth CV, Vintzileos AM, Abuhamad AZ. Electronic fetal heart rate monitoring and its relationship to neonatal and JANUARY 2012 American Journal of Obstetrics & Gynecology
e19
www.AJOG.org UMDNJ-Robert Wood Johnson Medical School New Brunswick, NJ 08903 [email protected] The authors report no conflict of interest.
REFERENCES 1. Philipp CS, Faiz A, Heit JA, et al. Evaluaton of a screening tool for bleeding disorders in a US multisite cohort of women with menorrhagia. Am J Obstet Gynecol 2011;204:209.e1-7. 2. Kirtava A, Crudder S, Dilley A, Lally C, Evatt B. Trends in clinical management of women with von Willebrand Disease: a survey of 75 women enrolled in haemophilia treatment centres in the United States. Hemophilia 2004;10:158-61. 3. Grimes DA, Schulz KF. Uses and abuses of screening tests. Lancet 2002;359:881-4. 4. Evans MI, Galen RS, Britt DW. Principles of screening. Semin Perinatol 2005;29:364-6. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2011.07.005
Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States TO THE EDITORS: The Journal recently published an article suggesting a causal association between electronic fetal monitoring (EFM) and decreased infant mortality.1 We have strong reservations regarding the ability of that paper to offer guidance regarding the effectiveness of EFM because it is inappropriate to use vital statistics data to make the leap from statistical association to causation. Several years ago, two of us contributed to a set of American Journal of Obstetrics and Gynecology commentaries discussing the reasonable use of secondary vital statistics data.2,3 Those commentaries raised important issues and limitations that should be considered, acknowledged, and addressed. The first issue is the potential inaccuracy of the EFM data. Validation of birth certificates has found that obstetric procedures, including EFM, are particularly poorly reported.4 Although random underreporting of EFM would bias estimates of the association between EFM and mortality toward finding no difference, it may be optimistic to assume that underreporting is random. We are aware of no study evaluating differential reporting of obstetric procedures, but it is plausible that reporting of intrapartum events may be less complete when, for example, an ill neonate is transferred shortly after birth.3 Differential reporting could bias the relative risk in either direction. The second issue is confounding. Even if EFM were perfectly reported, we doubt that the factors controlled for by Chen et al,1 maternal age, race/ethnicity, education, marital status, self-reported tobacco and alcohol use, and infant sex, are the most relevant characteristics to explain how the 11% of labors that were not monitored differed from the 89% that were. Of great concern is the inability to ascertain the clinical circumstances of the labors. Among the many unmeasured potentially confounding factors are precipitous delivery or delivery in settings without easy access e18
American Journal of Obstetrics & Gynecology JANUARY 2012
to EFM (and, perhaps, specialized obstetric care). These factors would be associated with both lack of EFM and adverse outcome. Lastly, there is inappropriate use of causal language and inference in the description and interpretation of these crosssectional administrative data. Within the limitations of birth certificate data, the paper by Chen et al1 may provide a helpful description of EFM use. However, it should not be used as a basis for clinical decision making, nor should the association between EFM and decreased infant mortality be deemed a causal one on the basis of this analysis. f Mark A. Klebanoff, MD, MPH Director Ohio Perinatal Research Network Department of Pediatrics The Ohio State University College of Medicine and Nationwide Children’s Hospital Columbus, OH 43205 [email protected] Amy M. Branum, PhD, MSPH Kenneth C. Schoendorf, MD, MPH Infant, Child, and Women’s Health Statistics Branch National Center for Health Statistics Centers for Disease Control and Prevention Hyattsville, MD 20782 Courtney D. Lynch, PhD, MPH Director of Reproductive Epidemiology Department of Obstetrics and Gynecology The Ohio State University College of Medicine Columbus, OH 43210 The findings and conclusions in this paper are those of the authors and do not necessarily represent the views of the National Center for Health Statistics, Centers for Disease Control and Prevention.
Letters to the Editors
www.AJOG.org REFERENCES 1. Chen HY, Chauhan SP, Ananth CV, Vintzileos AM, Abuhamad AZ. Electronic fetal heart rate monitoring and its relationship to neonatal and infant mortality in the United States. Am J Obstet Gynecol 2011;204: 491.e1-10. 2. Cahill AG, Macones GA. Vital considerations for the use of vital statistics in obstetrical research. Am J Obstet Gynecol 2006;194:909-10. 3. Schoendorf KC, Branum AM. The use of United States vital statistics in perinatal and obstetric research. Am J Obstet Gynecol 2006;194:911-5. 4. Dobie SA, Baldwin LM, Rosenblatt RA, Fordyce MA, Andrilla CHA, Hart LG. How well do birth certificates describe the pregnancies they report? The Washington State experience with low-risk pregnancies. Matern Child Health J 1998;2:145-54. © 2012 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2011.08.008
REPLY We are delighted that our article1 exploring the association between the utilization of electronic fetal monitoring (EFM) and risk of adverse infant morbidity and mortality has evinced interest from Klebanoff et al.2 At the outset, we were surprised to note that Klebanoff et al2 have expressed concerns regarding an evaluation of the benefits of EFM based on vital statistics data when they themselves, since 1992, have collectively published at least 36 articles that are based on the vital statistics data. This irony aside, let us address the primary concerns about our publication.1 First, Klebanoff et al2 worry that we inappropriately used the vital statistics data “to make the leap from statistical association to causation.” We do not. May we point out that the very first sentence of the abstract states the objective was “to examine the association between EFM and neonatal and infant mortality as well as neonatal morbidity?” In the study design portion of the abstract, we wrote the “estimate risk ratio for association between electronic fetal heart rate monitoring and mortality.” In the introduction, we noted that “the primary objective of this study was to examine the association between EFM during labor and corrected neonatal and infant mortality in the United States.” Although it is possible to draw causal inferences, our goal was to infer only associations in the article. However, it should be also noted that we found a significant dose-response relationship between gestational age and the number needed to treat with earlier gestations requiring the least number needed to treat. Second, Klebanoff et al2 argue about the “potential inaccuracy of the EFM data.” Under the section of strengths and weakness section of our article,1 the very first limitation we acknowledged was that “studies based on birth certificates have been criticized because of the quality of the data.” Nonetheless, it is noteworthy that our finding of significant increased rate of operative deliveries for fetal distress3 and decrease in neonatal seizures associated with EFM utilization is consistent with a metaanalysis of 12 randomized controlled trials (RCTs) on EFM.4 We do acknowledge that some degree of misclassification of EFM on vital statistics data is likely, but we wonder whether it really is possible that limitations of vital statistics
provide results concordant with RCTs when focused on morbidity and not on mortality. Third, Klebanoff et al2 are apprehensive about the role of unmeasured confounders on our findings. Although we did not specifically draw attention to the role of unmeasured confounders on the associations that we reported, it is very unlikely that a complete adjustment for “all possible confounders” would drive the strong associations of EFM use and early neonatal deaths and a low 5 minute Apgar score that we report toward the null. In addition, we underscore the congruity of our findings and that of earlier publications, including a metaanalysis of 12 RCTs.4 After careful reading of their concerns, we affirm that our data indicate what we concluded before: “In the United States, the use of EFM was associated with a substantial decrease in early neonatal mortality and morbidity.” We do welcome large and adequately powered RCTs to disprove our conclusions; like Freeman and Nageotte,5 we do not subscribe to the nihilistic view of the EFM and believe that the best evidence of the benefits of EFM may not come from the small RCTs but from f the largest observational study reported to date.1 Suneet P. Chauhan, MD Director, Maternal-Fetal Medicine Department of Obstetrics-Gynecology Eastern Virginia Medical School 825 Fairfax Ave. Norfolk, VA 23507 [email protected] Han-Yang Chen, MS Biostatistician Assistant Researcher Center for Urban Population Health University of Wisconsin School of Medicine and Public Health Milwaukee, WI 53233 Cande V. Ananth, PhD, MPH Professor of Reproductive Sciences Department of Obstetrics and Gynecology Columbia University Medical Center New York, NY 10032 Anthony M. Vintzileos, MD Chairman and Program Director Department of Obstetrics and Gynecology Winthrop University Hospital Mineola, NY 11501 Alfred Z. Abuhamad, MD Chairman Department of Obstetrics and Gynecology Eastern Virginia Medical School 825 Fairfax Ave. Norfolk, VA 23507 REFERENCES 1. Chen HY, Chauhan SP, Ananth CV, Vintzileos AM, Abuhamad AZ. Electronic fetal heart rate monitoring and its relationship to neonatal and JANUARY 2012 American Journal of Obstetrics & Gynecology
e19