Open access. Preterm birth, 90% of which occurs between 32 and <37 weeks’ gestation,1 2 is a complex heterogeneous syndrome interlinked with the stillbirth and intrauterine growth restriction syndromes.3 4 Its phenotypes are associated with different gains in neonatal weight,5 morbidity and mortality,6 and perhaps body composition, growth and development. Preterm birth is related to several aetiologies, although nearly 30% of all preterm births are not associated with any maternal/pregnancy conditions or fetal growth restriction.6 This group is, therefore, the target population for constructing postnatal growth standards for preterm infants.7 8 There is disagreement, however, about how best to monitor the postnatal growth of such a heterogeneous group of newborns. In fact, a systematic review identified 61 existing longitudinal charts for preterm infants, many with considerable limitations in gestational age estimation, body measurement, length of follow-up and description of feeding practices and morbidities.9