Gigs package -new egen extensions for international newborn and child growth standards

Understanding how and why child growth patterns have changed is necessary for characterizing global health inequalities. Sustainable development goal 3.2 aims to reduce preventable newborn deaths by at least 12 deaths per 1,000 live births and child deaths to 25 per 1,000 live births (WHO/UNICEF, 2019). However, large gaps remain in achieving these goals: currently 54 and 64 (of 194) countries will miss the targets for child (<5 years) and neonatal (<28 days) mortality, respectively (UN IGME, 2022). Because infant mortality is associated strongly with nonoptimal growth, accurate growth assessment using prescriptive growth standards is essential to reduce these mortality gaps.

A range of standards can be used to analyze infant growth: In newborns, size-for-gestational age analysis of different anthropometric measurements is possible using the Newborn Size standards from the International Fetal and Newborn Growth Consortium for the 21st Century (INTERGROWTH-21st) project (Villar et al., 2014). In infants, growth analysis depends on whether the child is born preterm or term: for term infants, the WHO Child Growth Standards are appropriate (WHO MGRS Group, 2006), whereas there are INTERGROWTH-21st standards for post-natal growth in preterm infants (Villar et al., 2018). Unfortunately, many researchers apply these standards incorrectly, which can lead to inappropriate interpretations of growth trajectories (Perumal et al., 2022).

As part of the Guidance for International Growth Standards (GIGS) project, we are making a range of these tools available in Stata to provide explicit, evidence-based functions through which these standards can be implemented in research and clinical care. We therefore introduce several egen extensions for converting between anthropometric measurements and centiles/z-scores in WHO and INTERGROWTH-21st standards. We also describe several egen functions that classify newborn size and infant growth according to international growth standards.

References:
Perumal, N., E. O. Ohuma, A. M. Prentice, P. S. Shah, A. Al Mahmud, S. E. Moore, D. E. Roth. 2022. Implications for quantifying early life growth trajectories of term-born infants using INTERGROWTH-21st newborn size standards at birth in conjunction with World Health Organization child growth standards in the postnatal period. Paediatric and Perinatal Epidemiology 6: 839–850.

United Nations Inter-agency Group for Child Mortality Estimation (UN IGME). 2023. Levels & Trends in Child Mortality: Report 2022, Estimates developed by the United Nations Inter-agency Group for Child Mortality Estimation, United Nations Children’s Fund, New York.

Villar, J., L. C. Ismail, C. G. Victora, E. O. Ohuma, E. Bertino, D. G. Altman, A. Lambert, A. T. Papageorghiou et al. 2014. International standards for newborn weight, length, and head circumference by gestational age and sex: The Newborn Cross-Sectional Study of the INTERGROWTH-21st Project. The Lancet 384(9946): 857–868.

Villar, J., F. Giuliani, Z. A. Bhutta, E. Bertino, E. O. Ohuma, L. C. Ismail, F. C. Barros, D. G. Altman, et al. 2015. Postnatal growth standards for preterm infants: The Preterm Postnatal Follow-up Study of the INTERGROWTH-21st Project. The Lancet Global Health 3(11): e681–e691.

WHO Multicentre Growth Reference Study Group. 2006. WHO Child Growth Standards based on length/height, weight and age. Acta Paediatrica Suppl. 450: 76–85.

WHO/UNICEF. 2019. WHO/UNICEF discussion paper: The extension of the 2025 maternal, infant and young child nutrition targets to 2030.https://data.unicef.org/resources/who-unicef-discussion-paper-nutrition-targets/ (accessed May 15th, 2023).