Joanne KatzAnne C.C. LeeNaoko KozukiJoy E. LawnSimon CousensHannah BlencoweMajid EzzatiZulfiqar A. BhuttaTanya MarchantBarbara A. WilleyLinda AdairFernando BarrosAbdullah H. BaquiParul ChristianWafaie FawziRogelio GonzalezJean HumphreyLieven HuybregtsPatrick KolsterenAroonsri MongkolchatiLuke C. MullanyRichard NdyomugyenyiJyh Kae NienDavid OsrinDominique RoberfroidAyesha SaniaChristentze SchmiegelowMariangela F. SilveiraJames TielschAnjana VaidyaSithembiso C. VelaphiCesar G. VictoraDeborah Watson-JonesRobert E. BlackJohns Hopkins Bloomberg School of Public HealthBrigham and Women's HospitalSave the Children USALondon School of Hygiene &amp; Tropical MedicineImperial College LondonThe Aga Khan UniversityThe University of North Carolina SystemUniversidade Federal de PelotasCentroHarvard School of Public HealthPontificia Universidad Catolica de ChileClinica Santa MariaZvitamboUniversiteit GentPrins Leopold Instituut voor Tropische GeneeskundeMahidol UniversityUganda Ministry of HealthClinica DavilaUniversidad de los Andes, SantiagoUCL Institute of Child HealthGeorge Washington UniversityKobenhavns UniversitetCopenhagen University HospitalUniversity of WitwatersrandNational Institutes of Medical Research2018-10-192018-10-192013-06-07The Lancet. Vol.382, No.9890 (2013), 417-4251474547X014067362-s2.0-84881183070https://repository.li.mahidol.ac.th/handle/20.500.14594/32301Background Babies with low birthweight (<2500 g) are at increased risk of early mortality. However, low birthweight includes babies born preterm and with fetal growth restriction, and not all these infants have a birthweight less than 2500 g. We estimated the neonatal and infant mortality associated with these two characteristics in low-income and middle-income countries. Methods For this pooled analysis, we searched all available studies and identified 20 cohorts (providing data for 2015019 livebirths) from Asia, Africa, and Latin America that recorded data for birthweight, gestational age, and vital statistics through 28 days of life. Study dates ranged from 1982 through to 2010. We calculated relative risks (RR) and risk differences (RD) for mortality associated with preterm birth (<32 weeks, 32 weeks to <34 weeks, 34 weeks to <37 weeks), small-for-gestational-age (SGA; babies with birthweight in the lowest third percentile and between the third and tenth percentile of a US reference population), and preterm and SGA combinations. Findings Pooled overall RRs for preterm were 6·82 (95% CI 3·56-13·07) for neonatal mortality and 2·50 (1·48-4·22) for post-neonatal mortality. Pooled RRs for babies who were SGA (with birthweight in the lowest tenth percentile of the reference population) were 1·83 (95% CI 1·34-2·50) for neonatal mortality and 1·90 (1·32-2·73) for post-neonatal mortality. The neonatal mortality risk of babies who were both preterm and SGA was higher than that of babies with either characteristic alone (15·42; 9·11-26·12). Interpretation Many babies in low-income and middle-income countries are SGA. Preterm birth affects a smaller number of neonates than does SGA, but is associated with a higher mortality risk. The mortality risks associated with both characteristics extend beyond the neonatal period. Differentiation of the burden and risk of babies born preterm and SGA rather than with low birthweight could guide prevention and management strategies to speed progress towards Millennium Development Goal 4 - the reduction of child mortality. © 2013 Elsevier Ltd.Mahidol UniversityMedicineArticleSCOPUS10.1016/S0140-6736(13)60993-9