Copyright © 2004 by the Johns Hopkins Bloomberg School of Public Health
ORIGINAL CONTRIBUTIONS |
On the Definition of Gestational-Age-specific Mortality
From the Division of Clinical Trials and Epidemiological Sciences, National Cancer Centre, Singapore.
The "fetuses at risk" concept of gestational-age-specific mortality proposed by Yudkin et al. (Lancet 1987;1:1192–4) and extended by various researchers is becoming popular in perinatal and pediatric epidemiology. However, the definitions using this concept have led to a puzzling phenomenon in which mortality rates appear to increase monotonically with advancing gestational age. While proponents of this concept have highlighted the rationale for using as the denominator the number of fetuses at risk rather than that of fetuses delivered at a particular gestational week, many have not discussed how the numerator is derived. This article reviews various definitions of gestational-age-specific mortality rates. It points out that the definitions based on the concept of Yudkin et al. are indicators of short-term risk only. Furthermore, the seemingly monotonic positive association between mortality rates and gestational age is a misinterpretation. All of the definitions are valid when used and interpreted correctly. The choice of which definition to adopt depends on the specific issues one attempts to address. Calls for abandoning the conventional definitions are not justified.
fetal death; gestational age; infant mortality; pregnancy outcome
Abbreviations: Abbreviations: SB, number of stillbirths; SBR, stillbirth rate; TB, total number of births.
CiteULike 
Connotea 
Del.icio.us What's this?
Related articles in Am. J. Epidemiol.:
- A Proportional Hazards Model with Time-dependent Covariates and Time-varying Effects for Analysis of Fetal and Infant Death
- Robert W. Platt, K. S. Joseph, Cande V. Ananth, Justin Grondines, Michal Abrahamowicz, and Michael S. Kramer
Am. J. Epidemiol. 2004 160: 199-206.[Abstract] [FREE Full Text] - Invited Commentary: What’s So Bad about Curves Crossing Anyway?
- Mark A. Klebanoff and Kenneth C. Schoendorf
Am. J. Epidemiol. 2004 160: 211-212.[Extract] [FREE Full Text] - Invited Commentary: Analysis of Gestational-Age-specific Mortality—On What Biologic Foundations?
- Allen J. Wilcox and Clarice R. Weinberg
Am. J. Epidemiol. 2004 160: 213-214.[Extract] [FREE Full Text] - Platt et al. Respond to the Two Invited Commentaries
- Robert W. Platt, K. S. Joseph, Cande V. Ananth, Justin Grondines, Michal Abrahamowicz, and Michael S. Kramer
Am. J. Epidemiol. 2004 160: 215-216.[Extract] [FREE Full Text]
This article has been cited by other articles:
|
|
 |
|
  G. C. S. Smith RE: "A PROPORTIONAL HAZARDS MODEL WITH TIME-DEPENDENT COVARIATES AND TIME-VARYING EFFECTS FOR ANALYSIS OF FETAL AND INFANT DEATH" Am. J. Epidemiol., January 1, 2005; 161(1): 100 - 100. [Full Text] [PDF]
|
|
|
|
|
|
R. W. Platt, K. S. Joseph, C. V. Ananth, J. Grondines, M. Abrahamowicz, and M. S. Kramer THE AUTHORS REPLY Am. J. Epidemiol., January 1, 2005; 161(1): 100 - 101. [Full Text] [PDF]
|
|
|
|
|
|
A. J. Wilcox and C. R. Weinberg Invited Commentary: Analysis of Gestational-Age-specific Mortality--On What Biologic Foundations? Am. J. Epidemiol., August 1, 2004; 160(3): 213 - 214. [Full Text] [PDF]
|
|