Growth patterns by birth size of preterm children born at 24-29 gestational weeks for the first 3 years.

Background: Concerns are prevalent about preterm infant long-term growth regarding plotting low on growth charts at discharge, stunting, underweight, high body fat and subsequent cardiometabolic morbidities.

Objectives: To examine (a) longitudinal growth patterns of extremely and very preterm infants to 3 years corrected age (CA) (outcome), categorised by their birthweight for gestational age: small, appropriate and large for gestational age (SGA, AGA and LGA, respectively) (exposure); and (b) the ability of growth faltering (<-2 z-scores) to predict suboptimal cognitive scores at 3 years CA.

Methods: Post-discharge head, length, weight and weight-4-length growth patterns of the PreM Growth cohort study infants born <30 weeks and < 1500 g, who had dietitian and multi-disciplinary support before and after discharge, were plotted against the World Health Organization growth standard. Infants with brain injuries, necrotising enterocolitis and bronchopulmonary dysplasia were excluded.

Results: Of the included 405 infants, the proportions of infants with anthropometric measures > - 2 z-scores improved with age. The highest proportions <-2 z-scores for length (24.2%) and weight (24.0%) were at 36 gestational weeks. The proportion with small heads was low by 0 months CA (1.8%). By 3 years CA, only a few children plotted lower than -2 z-scores for length, weight-4-length and weight (<6%). After zero months CA, high weight-4-length and body mass index > + 2 z-scores were rare (2.1% at 3 years CA). Those born SGA had higher proportions with shorter heights (16.7% vs. 5.2%) and lower weights (27.8% vs. 3.5%) at 3 years CA compared to those born AGA. The ability of growth faltering to predict cognitive scores was limited (AUROC 0.42, 95% CI 0.39, 0.45 to 0.52, 95% CI 0.41, 0.63).

Conclusions: Although children born <30 weeks gestation without major neonatal morbidities plot low on growth charts at 36 weeks CA most catch up to growth chart curves by 3 years CA.