BackgroundBoth very preterm (VP; i.e., gestational age <32 weeks) and very low birth weight (VLBW; i.e., birth weight <1,500 g) are used as inclusion criteria by studies on preterm birth. We aimed to quantify the impact of these entities on postnatal growth until final height.MethodsSubjects born VP and/or with VLBW from the Project On Preterm and Small-for-gestational-age infants cohort were classified as follows: (1) VP+/VLBW+ (n=495), (2) VP+/VLBW- (n=207), or (3) VP-/VLBW+ (n=296) infants. Anthropometric data were collected at birth, 3, 6, 12, and 24 months' corrected age, and at 5 and 19 years. At 19 years, 590/998 (59%) of the subjects enrolled in 1983 were followed up.ResultsBirth size was smallest in the VP-/VLBW+ group compared with the VP+/VLBW+ and VP+/VLBW- groups. During childhood, length, weight, and head circumference SD scores increased in the VP-/VLBW+ group, whereas SD scores in the VP+/VLBW+ and VP+/VLBW- groups either remained stable or decreased. Despite catch-up growth, VP-/VLBW+ infants remained the shortest and lightest at age 19.ConclusionClassification on the basis of VP and VLBW impacts growth, causing different growth patterns for infants born VP+/VLBW+, VP+/VLBW-, or VP-/VLBW+. For future studies, we recommend, at least for industrialized countries, including preterm infants based on gestational age.