Kidney health and blood pressure after very preterm birth: a cohort study at school age

Very preterm infants (VPI, < 32 weeks of gestation) are at increased risk of chronic kidney disease and hypertension in later life, and slight abnormalities of kidney function may precede clinically apparent disease. We explored kidney function and blood pressure (BP) at school age in VPI, and their association with perinatal and postnatal factors, including neonatal nutrition and growth.

All VPI included at birth in a historical cohort evaluating kidney function during the first month of life were eligible at follow-up (4-6 years). Standardized assessments included anthropometry, BP, cystatin-C, urea, plasma and urinary creatinine and electrolytes, and urinary albumin-to-creatinine ratio. Abnormal biological findings were defined as one among: estimated glomerular filtration rate (eGFR) < 90 mL/min/1.73 m², macroalbuminuria, or microalbuminuria.

We included 69 children (mean age 5.1 ± 0.3 years). Thirty-one (44.9%) had at least one abnormal finding: eGFR < 90 mL/min/1.73 m² (33.8%), macroalbuminuria (1.4%), microalbuminuria (10.1%). High systolic and diastolic pressure (dBP) occurred in 10.1% and 8.7% of children, respectively. No variables were associated with abnormal eGFR, microalbuminuria, or macroalbuminuria. High dBP was significantly associated with lower birth weight (BW), lower (BW) Z-score, higher weight Z-score at 36 weeks post-conception, and higher BMI at follow-up. This association remained significant after adjustment for gestational age.

Abnormal eGFR, microalbuminuria, macroalbuminuria, as well as 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 kidney and cardiovascular risk assessment in this population.