ArticlesMortality risk in preterm and small-for-gestational-age infants in low-income and middle-income countries: a pooled country analysis
Introduction
An estimated 20 million infants every year are born with low birthweight (LBW; <2500 g),1 and these infants have an increased risk mortality in the first year of life. The primary causes of LBW are preterm birth, intrauterine growth restriction (IUGR), or a combination of the two. Of 135 million children born in low-income and middle-income countries (LMICs) in 2010, an estimated 29·7 million were born both term and small-for-gestational-age (SGA), 10·9 million were born preterm and appropriate-for-gestational-age, and 2·8 million were born preterm and SGA.2 Risk factors and interventions to reduce the number of babies born SGA might differ from those to reduce the number of babies born preterm. The survival and growth patterns of preterm or growth-restricted newborn babies are not well described in LMICs and the contribution to mortality of non-LBW babies (≥2500 g) who are preterm or those with IUGR in such settings is unknown.
Few studies in LMICs have investigated differences in mortality by extent of prematurity, IUGR, or the two in combination,3, 4 or mortality risk in infants who are SGA stratified by gestational age.5, 6, 7, 8, 9, 10 Examination of the mortality risk by degree of prematurity and SGA as a proxy for IUGR might be crucial in understanding the attributable disease burden, especially because regions such as south Asia have a reported SGA prevalence of about 40%.11, 12 Such mortality risk estimates and attributable burden could enable the specific targeting of these disorders with appropriate interventions to more effectively save lives.
The Child Health Epidemiology Reference Group (CHERG) previously examined the risk of infant mortality associated with term-LBW as a proxy for IUGR.13 However, term-LBW excludes growth-restricted infants weighing more than 2500 g and high risk infants born both preterm and SGA, and such associations between mortality and SGA-non-LBW or SGA-preterm have not been well described in LMICs. With more population-based studies in LMICs now collecting data for gestational age in addition to birthweight, the CHERG identified an opportunity to assess the mortality risk of SGA and preterm on early neonatal, late neonatal, neonatal, post-neonatal, and infant mortality.
Section snippets
Dataset identification
We searched Medline, WHO regional databases (African Index Medicus, LILAS, EMRO), bibliographies of sentinel articles and reviews, and grey literature to identify potential datasets from low-income and middle-income countries that recorded data for gestational age and birthweight, and systematically recorded vital status from delivery through at least 28 days of life. The most recent search was done on Feb 22, 2010. We applied no no date or language restrictions. Search terms included “preterm
Results
We included 20 datasets with 2 015 019 livebirths from sub-Saharan Africa, Latin America, and south and southeast Asia, with gestational age available for 2 008 675 babies and both gestational age and birthweight available for 1 996 763 babies (table and appendix).4, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40 Study dates ranged from 1982 through to 2010. The Chilean national birth registry35 provided much of these data. The prevalence of preterm birth
Discussion
We identified a large percentage of infants who were SGA but not LBW or preterm (21% in Asia, 16% in Africa, and 4% in Latin America), although their mortality rates were lower than preterm infants or SGA-LBW infants. Although most LBW was in term and SGA babies in Asia and Africa, the majority of babies with LBW in Latin America were preterm. Preterm mortality risk associations were generally higher at all gestational age categories (late, moderate, and early preterm) than SGA (3% to <10% or
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