OBJECTIVE: To compare neonatal mortality associated with six novel vulnerable newborn types in 125.5 million live births across 15 countries, 2000-2020. DESIGN: Population-based, multi-country study. SETTING: National data systems in 15 middle- and high-income countries. METHODS: We used individual-level data sets identified for the Vulnerable Newborn Measurement Collaboration. We examined the contribution to neonatal mortality of six newborn types combining gestational age (preterm [PT] versus term [T]) and size-for-gestational age (small [SGA], <10th centile, appropriate [AGA], 10th-90th centile or large [LGA], >90th centile) according to INTERGROWTH-21st newborn standards. Newborn babies with PT or SGA were defined as small and T + LGA was considered as large. We calculated risk ratios (RRs) and population attributable risks (PAR%) for the six newborn types. MAIN OUTCOME MEASURES: Mortality of six newborn types. RESULTS: Of 125.5 million live births analysed, risk ratios were highest among PT + SGA (median 67.2, interquartile range [IQR] 45.6-73.9), PT + AGA (median 34.3, IQR 23.9-37.5) and PT + LGA (median 28.3, IQR 18.4-32.3). At the population level, PT + AGA was the greatest contributor to newborn mortality (median PAR% 53.7, IQR 44.5-54.9). Mortality risk was highest among newborns born before 28 weeks (median RR 279.5, IQR 234.2-388.5) compared with babies born between 37 and 42 completed weeks or with a birthweight less than 1000 g (median RR 282.8, IQR 194.7-342.8) compared with those between 2500 g and 4000 g as a reference group. CONCLUSION: Preterm newborn types were the most vulnerable, and associated with the highest mortality, particularly with co-existence of preterm and SGA. As PT + AGA is more prevalent, it is responsible for the greatest burden of neonatal deaths at population level.

Centre for Data Integration and Knowledge for Health Instituto Gonçalo Moniz Fiocruz Bahia Fundação Oswaldo Cruz Salvador Brazil

Centre of Research Excellence in Stillbirth Mater Research Institute The University of Queensland Brisbane Queensland Australia

Clinical Epidemiology Division Department of Medicine Solna Karolinska Institutet Stockholm Sweden

Department of Clinical Epidemiology Aarhus University and Aarhus University Hospital Aarhus N Denmark

Department of Data Analysis Institute of Health Information and Statistics of the Czech Republic Prague Czech Republic

Department of Obstetrics and Gynaecology Institute for the Care of Mother and Child Prague Czech Republic

Department of Obstetrics and Gynaecology University of British Columbia Vancouver British Columbia Canada

Department of Paediatrics and Adolescent Medicine American University of Beirut Beirut Lebanon

Department of Population Health Sciences College of Life Sciences University of Leicester Leicester UK

Department of Wellness and Health Catholic University of Uruguay Montevideo Uruguay

Directorate of Health Information Ministry of Health Mexico City Mexico

Faculty of Medicine and Health University of Sydney Sydney New South Wales Australia

Finnish Population Research Institute Väestöliitto Helsinki Finland

Hamad Medical Corporation Doha Qatar

Maternal Adolescent Reproductive and Child Health Centre London School of Hygiene and Tropical Medicine London UK

Mexican Society of Public Health Mexico City Mexico

Perined Utrecht The Netherlands

Pregnancy Birth and Child Health Team Public Health Scotland Edinburgh UK

Public Health Scotland Edinburgh UK

Queen's Management School Queen's University Belfast Belfast UK

School of Governance Law and Society Estonian Institute for Population Studies Tallinn University Tallinn Estonia

School of Natural and Built Environment Queen's University Belfast Belfast UK

Usher Institute University of Edinburgh Edinburgh UK

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Vulnerable newborn types: Analysis of population-based registries for 165 million births in 23 countries, 2000-2021

Neonatal mortality risk of large-for-gestational-age and macrosomic live births in 15 countries, including 115.6 million nationwide linked records, 2000-2020