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Discussion: ‘Infant death among Ohio residents’ by Donovan et al
Journal Club Roundtable
www. AJOG.org
Discussion: ‘Infant death among Ohio residents’ by Donovan et al In the roundtable that follows, clinicians discuss a study published in this issue of the Journal in light of its methodology, relevance to practice, and implications for future research. Article discussed: Donovan EF, Besl J, Paulson J, et al, for the Ohio Perinatal Quality Collaborative. Infant death among Ohio resident infants born at 32 to 41 weeks of gestation. Am J Obstet Gynecol 2010;203:58.e1-5.
DISCUSSION QUESTIONS
Were the objectives of the study clearly defined?
What were the key study findings?
What are the strengths of the study?
Can you identify potential sources of bias? Are the study results applicable to your clinical practice? How might you address the study question differently?
From the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, University of AlabamaBirmingham School of Medicine, Birmingham, AL: Moderator Alan T. N. Tita, MD, PhD Assistant Professor Discussants Luisa A. Wetta, MD Fellow Elizabeth Bates, MD Fourth-Year Resident Amy Doss, MD Third-Year Resident Jamie L. Erwin, MD Second-Year Resident 0002-9378/$36.00 © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.04.005
See related article, page 58 For a summary and analysis of this discussion, see page 86
e8
I NTRODUCTION Timing delivery so that the best possible outcome is achieved remains a critical issue in contemporary obstetrics. Preterm birth, a major cause of infant morbidity, is also responsible for over one-third of infant deaths in the United States, and its prevalence continues to climb.1 This trend is partly due to an increase in indicated or elective births beyond 32 weeks, especially late preterm births at 34 weeks’ gestation and above.1,2 Early preterm births, also on the rise, are particularly likely to result in adverse neonatal outcomes.1,3 Initiatives to optimize gestational age at delivery can contribute substantially to improved neonatal and infant outcomes. Luisa A. Wetta, MD, Alan T. N. Tita, MD, PhD, and Todd R. Jenkins, MD, Associate Editor
S TUDY D ESIGN Tita: Welcome to the American Journal of Obstetrics & Gynecology Journal Club. Today, we are discussing an article by Donovan et al. Were the purpose and objectives of the study clearly defined? Erwin: They were. Overall, the purpose was to generate data for evaluation of an Ohio public health initiative designed to reduce prematurity-related adverse health outcomes. The objective, more specifically, was to determine infant mortality rates adjusted by gestational age at delivery. So we’re really looking at how the rates vary across different gestational ages. Tita: The study obviously focused on the population in Ohio. What were the key study findings, and were all relevant outcomes considered? Doss: The study showed that adjusted infant mortality rates decreased as ges-
American Journal of Obstetrics & Gynecology JULY 2010
tational age increased from 32 weeks to 40 weeks (12 per 1000 at 32–33 weeks vs 2 per 1000 at 39 – 40 weeks). This is not surprising—the lower the gestational age, the higher the infant mortality rate. The authors also assessed time to mortality, and the earlier the gestational age, the sooner infant mortality occurred. However, they did not look at fetal deaths or how that would affect the overall perinatal/infant mortality outcome. Although it’s likely a small number of fetal deaths occurred, it would be useful to know that reduced infant mortality associated with delivery at a later gestational age was not outweighed by fetal deaths. They also did not look at infant morbidity due to respiratory distress syndrome and other major infant morbidities. Tita: In your view, aside from fetal deaths and neonatal morbidity, were there other relevant outcomes that were not considered? Doss: No. Perhaps these were not available in their data source. Tita: What are the strengths of this study? Bates: First, the study was a large population-based study involving over 400,000 subjects. In addition, the authors were able to look at over 90% of the available target population, with very few subjects excluded. Tita: Yes, they were unable to include about 0.6% of the population because age of death was unavailable. What about potential sources of bias and their likely impact on study results? Bates: In my view, there were 2 major sources of bias. Of course, with a retrospective database study of this nature, information bias is likely for a range of
www.AJOG.org variables, including gestational age. Bias in gestational age data could influence study results in either direction—probably the adjusted effects would be underestimated if such errors occurred randomly. Confounding by additional risk factors for infant death and early delivery that had not been controlled for could also introduce bias. Also, infants with birth defects were included, and their risk for infant death was disproportionately higher— excluding them or perhaps stratifying results by absence of birth defects might have been preferable. Tita: You are suggesting that, since mortality among infants with birth defects was so high compared with the rest of the study population, this group be looked at separately? Bates: Yes.
C ONCLUSIONS Tita: Are the results applicable to your clinical practice? Tita: I will take this one. I think, yes, this study provides further information that
Journal Club Roundtable will be helpful in counseling patients about the importance of not delivering early, that is, prior to 39 weeks, if delivery is not indicated for maternal or fetal reasons. However, there is another potential benefit that is not applicable to my practice but to Ohio and the Ohio-based initiative. This study provides some baseline numbers in terms of infant mortality rates. These can be used to monitor the success of the initiative, specifically, to see whether the mortality rate goes down and whether nonindicated early deliveries are reduced. Tita: Given the opportunity and the resources to address these same study questions, what would you do differently? Wetta: Well, I think it’s probably not feasible to prospectively identify and then follow longitudinally the large number of patients needed for a study of infant mortality. In any case, I would ascertain and study fetal deaths or stillbirths, as well as infant mortality rates. And one could also study infant morbidity at the same time.
Tita: Any other comments about the study in general? Overall, is it useful, not useful? Erwin: I think it’s useful, because, as has been discussed, timing of delivery is a daily issue in practice. Many times, patients are anxious and ask why they can’t be delivered sooner, and this article adds to the accumulating information supporting the benefit of delaying and not delivering prematurely or early without a clear fetal or maternal reason. Tita: Any other comments? So overall, this article provides useful information from both a clinical and public health perspective. Thank you all very much for participating. f REFERENCES 1. Martin JA, Hamilton BE, Sutton PD, et al. Births: final data for 2006. Natl Vital Stat Rep 2009;57:1-102. 2. Reddy UM, Ko CW, Raju TN, Willinger M. Delivery indications at late-preterm gestations and infant mortality rates in the United States. Pediatrics 2009;124:234-40. 3. Tita AT, Landon MB, Spong CY, et al; Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network. Timing of elective repeat cesarean delivery at term and neonatal outcomes. N Engl J Med 2009;360:111-20.
JULY 2010 American Journal of Obstetrics & Gynecology
e9
www. AJOG.org
Discussion: ‘Infant death among Ohio residents’ by Donovan et al In the roundtable that follows, clinicians discuss a study published in this issue of the Journal in light of its methodology, relevance to practice, and implications for future research. Article discussed: Donovan EF, Besl J, Paulson J, et al, for the Ohio Perinatal Quality Collaborative. Infant death among Ohio resident infants born at 32 to 41 weeks of gestation. Am J Obstet Gynecol 2010;203:58.e1-5.
DISCUSSION QUESTIONS
Were the objectives of the study clearly defined?
What were the key study findings?
What are the strengths of the study?
Can you identify potential sources of bias? Are the study results applicable to your clinical practice? How might you address the study question differently?
From the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, University of AlabamaBirmingham School of Medicine, Birmingham, AL: Moderator Alan T. N. Tita, MD, PhD Assistant Professor Discussants Luisa A. Wetta, MD Fellow Elizabeth Bates, MD Fourth-Year Resident Amy Doss, MD Third-Year Resident Jamie L. Erwin, MD Second-Year Resident 0002-9378/$36.00 © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.04.005
See related article, page 58 For a summary and analysis of this discussion, see page 86
e8
I NTRODUCTION Timing delivery so that the best possible outcome is achieved remains a critical issue in contemporary obstetrics. Preterm birth, a major cause of infant morbidity, is also responsible for over one-third of infant deaths in the United States, and its prevalence continues to climb.1 This trend is partly due to an increase in indicated or elective births beyond 32 weeks, especially late preterm births at 34 weeks’ gestation and above.1,2 Early preterm births, also on the rise, are particularly likely to result in adverse neonatal outcomes.1,3 Initiatives to optimize gestational age at delivery can contribute substantially to improved neonatal and infant outcomes. Luisa A. Wetta, MD, Alan T. N. Tita, MD, PhD, and Todd R. Jenkins, MD, Associate Editor
S TUDY D ESIGN Tita: Welcome to the American Journal of Obstetrics & Gynecology Journal Club. Today, we are discussing an article by Donovan et al. Were the purpose and objectives of the study clearly defined? Erwin: They were. Overall, the purpose was to generate data for evaluation of an Ohio public health initiative designed to reduce prematurity-related adverse health outcomes. The objective, more specifically, was to determine infant mortality rates adjusted by gestational age at delivery. So we’re really looking at how the rates vary across different gestational ages. Tita: The study obviously focused on the population in Ohio. What were the key study findings, and were all relevant outcomes considered? Doss: The study showed that adjusted infant mortality rates decreased as ges-
American Journal of Obstetrics & Gynecology JULY 2010
tational age increased from 32 weeks to 40 weeks (12 per 1000 at 32–33 weeks vs 2 per 1000 at 39 – 40 weeks). This is not surprising—the lower the gestational age, the higher the infant mortality rate. The authors also assessed time to mortality, and the earlier the gestational age, the sooner infant mortality occurred. However, they did not look at fetal deaths or how that would affect the overall perinatal/infant mortality outcome. Although it’s likely a small number of fetal deaths occurred, it would be useful to know that reduced infant mortality associated with delivery at a later gestational age was not outweighed by fetal deaths. They also did not look at infant morbidity due to respiratory distress syndrome and other major infant morbidities. Tita: In your view, aside from fetal deaths and neonatal morbidity, were there other relevant outcomes that were not considered? Doss: No. Perhaps these were not available in their data source. Tita: What are the strengths of this study? Bates: First, the study was a large population-based study involving over 400,000 subjects. In addition, the authors were able to look at over 90% of the available target population, with very few subjects excluded. Tita: Yes, they were unable to include about 0.6% of the population because age of death was unavailable. What about potential sources of bias and their likely impact on study results? Bates: In my view, there were 2 major sources of bias. Of course, with a retrospective database study of this nature, information bias is likely for a range of
www.AJOG.org variables, including gestational age. Bias in gestational age data could influence study results in either direction—probably the adjusted effects would be underestimated if such errors occurred randomly. Confounding by additional risk factors for infant death and early delivery that had not been controlled for could also introduce bias. Also, infants with birth defects were included, and their risk for infant death was disproportionately higher— excluding them or perhaps stratifying results by absence of birth defects might have been preferable. Tita: You are suggesting that, since mortality among infants with birth defects was so high compared with the rest of the study population, this group be looked at separately? Bates: Yes.
C ONCLUSIONS Tita: Are the results applicable to your clinical practice? Tita: I will take this one. I think, yes, this study provides further information that
Journal Club Roundtable will be helpful in counseling patients about the importance of not delivering early, that is, prior to 39 weeks, if delivery is not indicated for maternal or fetal reasons. However, there is another potential benefit that is not applicable to my practice but to Ohio and the Ohio-based initiative. This study provides some baseline numbers in terms of infant mortality rates. These can be used to monitor the success of the initiative, specifically, to see whether the mortality rate goes down and whether nonindicated early deliveries are reduced. Tita: Given the opportunity and the resources to address these same study questions, what would you do differently? Wetta: Well, I think it’s probably not feasible to prospectively identify and then follow longitudinally the large number of patients needed for a study of infant mortality. In any case, I would ascertain and study fetal deaths or stillbirths, as well as infant mortality rates. And one could also study infant morbidity at the same time.
Tita: Any other comments about the study in general? Overall, is it useful, not useful? Erwin: I think it’s useful, because, as has been discussed, timing of delivery is a daily issue in practice. Many times, patients are anxious and ask why they can’t be delivered sooner, and this article adds to the accumulating information supporting the benefit of delaying and not delivering prematurely or early without a clear fetal or maternal reason. Tita: Any other comments? So overall, this article provides useful information from both a clinical and public health perspective. Thank you all very much for participating. f REFERENCES 1. Martin JA, Hamilton BE, Sutton PD, et al. Births: final data for 2006. Natl Vital Stat Rep 2009;57:1-102. 2. Reddy UM, Ko CW, Raju TN, Willinger M. Delivery indications at late-preterm gestations and infant mortality rates in the United States. Pediatrics 2009;124:234-40. 3. Tita AT, Landon MB, Spong CY, et al; Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units Network. Timing of elective repeat cesarean delivery at term and neonatal outcomes. N Engl J Med 2009;360:111-20.
JULY 2010 American Journal of Obstetrics & Gynecology
e9