Kidney health and blood pressure after very preterm birth. A cohort study at school age

Background Very preterm infants (VPI, < 32 weeks of gestation) are at increased risk of chronic kidney disease and hypertension in later life, and biological abnormalities of kidney function may precede clinically apparent disease. We evaluated kidney function and blood pressure (BP) at school age in VPI and explored their association with perinatal and postnatal factors, including neonatal nutrition and growth. Methods VPI included since birth in a cohort to evaluate kidney function were followed-up at 4–6 years. Standardized assessments included anthropometry, BP, cystatin-C, urea, plasma and urinary creatinine and electrolytes, and urinary albumin-to-creatinine ratio. Biological kidney abnormalities were defined as one among: estimated glomerular filtration rate (eGFR) < 90 mL/min/1.73 m², macroalbuminuria, or microalbuminuria. Results In total, 69 children (mean age 5.1 ± 0.3 years) attended follow-up and 39 (56.5%) had at least one biological kidney abnormality: eGFR < 90 mL/min/1.73 m² (33.8%), macroalbuminuria (1.4%), or microalbuminuria (26.1%). Hight systolic and diastolic pressure (dBP) occurred in 10.1% and 8.7% of children, respectively. Any neonatal variable, including nutritional intakes, was associated with biological kidney abnormalities. High dBP was significantly associated with lower birth weight, lower birth weight Z-score, higher weight Z-score at 36 weeks post-conception, and higher BMI at follow-up, and the association remained significant after adjustment for gestational age. Conclusions Biological kidney abnormalities and elevated BP are frequent in ex-VPI at school age. The association between high dBP and rapid early catch-up growth underscores the need to monitor growth trajectories as part of early renal and cardiovascular risk assessment in this population.