Inclusion of Non-Viable Neonates in the Birth Record and Its Impact on Infant Mortality Rates in Shelby County, Tennessee, USA

Bryan L Williams,Melina S Magsumbol

doi:10.4081/pr.2010.e1

Bryan L Williams, Melina S Magsumbol

Open Access

https://doi.org/10.4081/pr.2010.e1

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Abstract

Rates of infant death are one of the most common indicators of a population's overall health status. Infant mortality rates (IMRs) are used to make broad inferences about the quality of health care, effects of health policies and even environmental quality. The purpose of our study was threefold: i) to examine the characteristics of births in the area in relation to gestational age and birthweight; ii) to estimate infant mortality using variable gestational age and/or birthweight criteria for live birth, and iii) to calculate proportional mortality ratios for each cause of death using variable gestational age and/or birthweight criteria for live birth. We conducted a retrospective analysis of all Shelby County resident-linked birth and infant death certificates during the years 1999 to 2004. Descriptive test statistics were used to examine infant mortality rates in relation to specific maternal and infant risk factors. Through careful examination of 1999–2004 resident-linked birth and infant death data sets, we observed a disproportionate number of non-viable live births (≤20 weeks gestation or ≤350 grams) in Shelby County. Issuance of birth certificates to these non-viable neonates is a factor that contributes to an inflated IMR. Our study demonstrates the complexity and the appropriateness of comparing infant mortality rates in smaller geographic units, given the unique characteristics of live births in Shelby County. The disproportionate number of pre-viable infants born in Shelby County greatly obfuscates neonatal mortality and de-emphasizes the importance of post-neonatal mortality.

Highlights

IntroductionLike other types of mortality, infant mortality rates (IMRs) are confounded by case definitions, population structure and reporting accuracy.[1,2,3,4,5,6,7,8,9,10,11,12,13] Birth and death certificates are often incomplete and inaccurate.[8,9,10,14,15,16,17] For example, congenital anomalies are frequently underreported, while the number of prenatal visits is often over-reported.[9,10,17] Valid inferences about birth outcomes from these data sources are difficult to make because of their inherent unreliability
For 2002-2003, the infant mortality rates (IMRs) returned to its previous level of 6.84 per 1,000 live births
In Shelby County, LMP is much less likely to be reported on the birth certificate than is the clinical estimate

Summary

Introduction

Like other types of mortality, infant mortality rates (IMRs) are confounded by case definitions, population structure and reporting accuracy.[1,2,3,4,5,6,7,8,9,10,11,12,13] Birth and death certificates are often incomplete and inaccurate.[8,9,10,14,15,16,17] For example, congenital anomalies are frequently underreported, while the number of prenatal visits is often over-reported.[9,10,17] Valid inferences about birth outcomes from these data sources are difficult to make because of their inherent unreliability. The United States IMRs from 2001 to 2002 increased to 6.95 deaths per 1,000 live births, the first increase seen since 1958. 49% of infant deaths in 2003 occurred among infants with very low birthweight (less than 1500 g). Were these real trends or artifacts of the data collection process?

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