Table 1. Summary of characteristics of growth charts explored.

Characteristics	Population	Customised	Intergrowth
Population used for development	Swedish population (internally developed using Swedish Medical Birth Registry population available to this study, n = 233,379)	Combination of registries and datasets for multiple countries (www.gestation.net)	Pooled data from single-centre cohorts in eight countries (n = 20,486)
Estimated fetal weight versus birth weight	Birth-weight chart	Term optimal weight was developed using birth weight. In the preterm period, fetal weight has been estimated using a proportionality formula based on the Hadlock’s fetal weight equation	Birth-weight chart
Descriptive versus prescriptivea	Retrospective development of a descriptive chart	Retrospective development of a prescriptive chart	Prospective development of a prescriptive chart
Adjustment/covariates	Gestational age and infant sex	Maternal ethnicity, height and weight, parity, gestational age, and infant sex	Gestational age and infant sex
Underlying principle	Infants in a given population should have a similar growth potential	Infant growth potential is physiologically influenced by maternal and fetal factors	Infants worldwide should have a similar growth potential

^aDescriptive charts are also known as ‘references’ and describe the estimated fetal weight or birth weight in the whole sample, including women with comorbidities such as preeclampsia or gestational diabetes. Prescriptive charts are also known as standards and aim to report growth in presumably healthy individuals, usually excluding the effect of comorbidities, smoking, and socioeconomic status (amongst other factors). The factors used to presume a healthy population may vary between charts.