Catch-up growth in the first two years of life in Extremely Low Birth Weight (ELBW) infants is associated with lower body fat in young adolescence.

Aim: To investigate growth patterns and anthropometrics in former extremely low birth weight (ELBW, <1000 g) children and link these outcomes to neurocognition and body composition in childhood.

Methods: ELBW children were examined at birth (n = 140), at 9 and 24 months (n≥96) and at approximately 11 years within the framework of the PREMATCH (PREMATurity as predictor children's of Cardiovascular and renal Health) case-control (n = 93-87) study. Regional growth charts were used to convert anthropometrics into Z-scores. Catch-up growth in the first two years of life was qualified as present if ΔZ-score >0.67 SDS. At 11 years, anthropometrics, neurocognitive performance, body composition, grip strength and puberty scores were assessed.

Results: ELBW neonates displayed extra-uterine growth restriction with mean Z-scores for height, weight and head circumference of -0.77, -0.93 and -0.46 at birth, -1.61, -1.67 and -0.72 at 9 months, -1.22, -1.61 and -0.84 at 24 months, and -0.42, -0.49 and -1.09 at 11 years. ELBW children performed consistently worse on neurocognitive testing with an average intelligence quotient equivalent at 11 years of 92.5 (SD 13.1). Catch-up growth was not associated with neurocognitive performance. Compared to controls, ELBW cases had lower grip strength (13.6 vs. 15.9 kg) and percentage lean body weight (75.1 vs. 80.5%), but higher body fat (24.6 vs. 19.2%) and advanced puberty scores at 11 years (all P≤0.025). Catch-up growth for weight and height in the first two years of life in cases was associated with a lower percentage body fat compared to cases without catch-up growth (16.8% catch-up growth for weight vs. 25.7%, P<0.001; 20.9% catch-up for height vs. 25.8%, P = 0.049).

Conclusions: In young adolescence, former ELBW children still have difficulties to reach their target height. Compared to normal birth weight controls, ELBW adolescents show lower neurocognitive performance and grip strength and a higher percentage body fat, a potential risk factor for adverse health outcomes in adulthood. Our key finding is that catch-up growth in ELBW children in the first two years of life is associated with a lower percentage body fat and is therefore likely to be beneficial.