6. Incorporating Deaths Near the Time of Birth into Estimates of the Global Burden of Disease

Stillbirths and Neonatal Mortality in the Context of the Global Burden of Disease

This section first introduces the nomenclature used throughout the chapter. It then provides estimates of deaths and death rates that highlight stillbirths and neonatal deaths and discusses deaths by cause at different ages.

Nomenclature

This chapter follows standard usage where possible, but extends or tightens it as needed. Stillbirth refers to the birth of a dead fetus weighing more than 1,000 grams up to 0.25 years (13 weeks) prior to the expected time of birth (corresponding to 27 weeks of gestational age). Total births are the sum of the number of live births and of stillbirths. Stillbirths are conventionally divided into two categories, antepartum stillbirths, when a fetus dies before the onset of labor, and intrapartum stillbirths, when fetal death occurs during labor. The term fresh stillbirths denotes fetuses born dead but with intact skin, which are assumed to have died less than 12 hours before birth and serve as an observable surrogate measure for intrapartum stillbirths. Individuals younger than 28 days are in the neonatal period and younger than 1 year are infants. The neonatal period is divided into the early neonatal period, which refers to birth to less than 7 days old, and the remaining late neonatal period. The postneonatal period extends from 28 days to under 1 year. Child in this chapter refers to an individual from age one to under age five. (In some other usage, however, child refers to all individuals under age five).

We use standard demographic terminology to indicate death rates at different ages, that is, _xq_y refers to the probability that an individual aged y will die before reaching age y + x and is usually estimated using cross-sectional observations of age-specific mortality rates for individual ages in the age range y to y + x. Using this terminology, the mortality rate for those under one year old (or the infant mortality rate) is ₁q₀. We extend this terminology to define the complete under one mortality rate as _1.25q_-.25, the child mortality rate as ₄q₁,¹ the under five mortality rate as ₅q₀, the stillbirth rate as _.25q_-.25, the neonatal mortality rate as _.077q₀, and the complete under five mortality rate as _5.25q_-.25. This chapter uses age-specific mortality rates for 2001.

Numbers of Deaths and Death Rates

In 2001, approximately 10.6 million children born alive died before their fifth birthday (8.2 percent of births). Of these deaths, 3.9 million occurred during the neonatal period, that is, under the age of 28 days. Another 3.3 million stillborn children remained outside the vital registration systems of most countries (WHO 2005a). When stillbirths are included among deaths, about half of all deaths of children under five occur under the age of 28 days.

Table 6.1 provides estimates of the numbers of stillbirths in 2001, with numbers broken down by World Bank income categories. The stillbirth numbers in the table come from rates estimated by the World Health Organization (WHO) (WHO 2005a) applied to the birth numbers reported in the table. The table shows that in 2001, the high-income countries (those with a gross national income per capita of more than US $9,076 in 2002) had 11.37 million live births and the low-and middle-income countries had 118.51 million live births.

Table 6.2 provides an age breakdown of deaths among children under five, again with a breakdown by World Bank income category. Early neonatal deaths account for 75 percent of all neonatal deaths. The eight-day period encompassing intrapartum stillbirths and early neonatal deaths accounts for almost 30 percent of the 13.9 million deaths occurring under the age of five. Thus, as shown in figure 6.1 for the low- and middle-income countries, roughly a quarter of the deaths under age five occur in each of the following categories: stillbirths, neonatal deaths, postneonatal infant deaths, and child deaths.
[Figure 6.1]

Three recent studies provide extensive literature reviews and model-based estimates of the number of stillbirths and neonatal deaths that extend the WHO estimates used here (WHO 2005a). Lawn, Shibuya, and Stein (2005, tables A-J) focus on intrapartum stillbirths and intrapartum-related neonatal deaths. Stanton and others (forthcoming) provide estimates of the number of stillbirths for 190 countries and Hill (forthcoming) provides estimates for neonatal deaths. The midpoints of their fairly wide confidence intervals accord with the numbers we use.

Table 6.3 shows death rates, expressed per 1,000 live births, that correspond to the death totals in table 6.2. Column (c), for example, shows an under one or infant mortality rate (₁q₀) for low- and middle-income countries of 64 per 1,000. Column (d) shows the effect of including stillbirths to give the complete under one mortality rate (_1.25q_-.25), which is markedly higher at 89 per 1,000 live births. By including stillbirths and providing relatively fine-grained age breakdowns, table 6.3 provides a more comprehensive set of estimates of mortality rates under age five than has hitherto been available. The wide confidence interval that needs to be attached to the estimates (Stanton and others forthcoming) indicates both the need for caution when using these numbers and the importance of further research. Nevertheless, the estimates in table 6.3 are reasonable given currently available information.

Deaths by Cause

Estimates of the total number of deaths in different age groups provide a starting point for breaking those totals down into deaths by cause. This task inevitably involves some degree of arbitrariness because of problems with classifying multiple causes of death or underlying versus proximal causes. That said, available data from vital registration, sentinel surveillance, and verbal autopsy can provide reasonable approximations for most causes. Chapter 3 provides background on how this was done and generates the death by cause estimates used throughout this book.

We use the estimates from chapter 3 for deaths by cause in the newborn through age four age group and aggregate chapter 3 data on age groups over age five into a single category of deaths for those age five and older. In their preparatory work for chapter 3, its authors estimated cause-specific breakdowns of deaths under age five both for infant deaths and for deaths from age one through age four, that is, deaths occurring at one year of age or older but under age five, and we have used their data in this chapter. Table 6.4 presents this information on deaths by cause aggregated, as previously indicated, into 35 groups of conditions rather than the 136 used in chapter 3.

The aggregate numbers for neonatal deaths and for stillbirths come from WHO (2005a) as reported in table 6.2 (see also WHO 2005b, pp. 170-71). Table 6.4 breaks down neonatal deaths into six causes: diarrheal diseases, tetanus, respiratory infections, low birthweight (essentially preterm birth), birth asphyxia and birth trauma, and congenital anomalies.² The estimates by cause were generated for WHO's Child Health Epidemiology Reference Group (CHERG) (see Bryce and others 2005 for a comprehensive presentation of data sources and methods of estimation). WHO (2005b, annex table 4) provides a summary of the numbers.

For the most part, the neonatal death categories used by CHERG align with the categories used by the GBD assessment in chapter 3; however, note the following exceptions:

• CHERG includes a pneumonia and sepsis category, which accounts for 26 percent of neonatal deaths globally and 27 percent in low- and middle-income countries. The GBD categories include respiratory infections (category I.B in our tables), which account for 1.945 million deaths worldwide in the age group 0-4. We allocate all the CHERG-estimated deaths from the combined category sepsis and pneumonia to the neonatal age group's respiratory infections category in order to remain as consistent as possible with the GBD framework in chapter 3. A number of studies have estimated the percentage of the broad category sepsis and pneumonia that is pneumonia with a wide range of findings (see, for example, Bhutta and others 2004 and Bhutta, Ali, and Wajid 2004). Even with blood cultures and chest x-rays, one cannot say for sure if a newborn has sepsis or pneumonia or both, and in any case, the treatment is the same, so one programmatic category is currently appropriate (Lawn, Cousens, and Wilczynska forthcoming).

• CHERG's percentage of neonatal deaths due to tetanus (7 percent) exceeds the GBD estimate for all infant deaths from tetanus but is very close to WHO and GAVI estimates for the year 2000 of 220,000. In keeping with this chapter's spirit of staying as close as possible to GBD estimates from chapter 3, we remain within the GBD envelope for the under-five age group and, as a first approximation, allocate all under one tetanus deaths to the neonatal period. However, while remaining within the under five GBD envelope for tetanus, we have modified, in this case only, the (unpublished) GBD age breakdown between ages 0-1 and 1-4 to allocate 90 percent of under five tetanus deaths to under age one (see table 6.4, note a). The difference between the CHERG and WHO with the GBD estimates for tetanus deaths is substantial and is clearly a priority area for further work.

• The GBD work uses the category low birthweight, which is an outcome of either preterm birth or intrauterine growth retardation. Preterm birth is a major cause of neonatal death. Again in the spirit of remaining within the GBD framework, we allocate preterm births to the low birthweight GBD category. This should not cause confusion as long as it is understood that, for neonatal deaths, low birthweight refers almost entirely to preterm birth. The quantitative importance of preterm birth suggests that this is another category that could be presented separately in the next GBD effort.

We are not aware of any effort to aggregate data on causes of stillbirths that parallels the CHERG effort for neonatal deaths, hence the GBD calculations in this chapter do not attempt to allocate stillbirths by cause. However, even though this chapter does not attempt a review of the CHERG type of the causes of stillbirth, we can advance a few tentative hypotheses. First, an important cause of stillbirth is intrapartum complications. A recent systematic analysis of intrapartum stillbirths gives estimates for 192 countries based on 73 study populations (52 countries, n = 46,779 [73 populations]) suggesting that 1.02 million intrapartum stillbirths (uncertainty 0.66-1.48 million) occur annually, accounting for 26 percent of global stillbirths. Second, congenital anomalies constitute an important cause of antepartum stillbirth. Third, sexually transmitted diseases and other infections cause antepartum stillbirth, but systematic global estimates are currently limited.

Our categorization of neonatal deaths within the GBD framework has been deliberately conservative in that where interpretation was in any way uncertain, we assigned deaths to the not allocated category. We expect future efforts to be able to substantially reduce the not allocated component for both stillbirths and neonatal deaths, but doing so will require both improved empirical information and modification of the current GBD framework to include classifications important for deaths near the time of birth. Until such improvements are possible, table 6.4 provides a plausible extension of the GBD cause of death framework to include causes of infant and neonatal deaths.