RESUMEN
BACKGROUND/OBJECTIVES: Maternal vitamin D deficiency during pregnancy may influence offspring kidney health. We aimed to examine the associations of 25-hydroxyvitamin D (25(OH)D) blood levels during fetal life with kidney outcomes at school age. SUBJECTS/METHODS: This study was embedded in a population-based prospective cohort study among 4212 mother-child pairs. We measured maternal second trimester (18-25 weeks) and fetal cord blood (at birth) 25(OH)D levels. At a median age of 6.0 years, we measured children's combined kidney volume, glomerular filtration rate (eGFR) from creatinine and cystatin C serum levels, and microalbuminuria from albumin and creatinine urine levels. RESULTS: Of all mothers, 21.9% had severely deficient levels (25(OH)D <25.0 nmol/l), 25.7% had deficient levels (25.0-49.9 nmol/l), 25% had sufficient levels (50.0-74.9 nmol/l) and 27.4% had optimal levels (⩾75.0 nmol/l). Maternal 25(OH)D levels were not consistently associated with childhood combined kidney volume. Higher maternal 25(OH)D levels were associated with lower childhood eGFR (difference -0.94 ml/min per 1.73 m(2) (95% confidence interval, -1.73; -0.15) per 1 standard deviation (s.d.) increase in 25(OH)D). Maternal 25(OH)D levels were not associated with microalbuminuria. Cord blood 25(OH)D levels were not associated with childhood kidney outcomes. The associations of maternal 25(OH)D levels with childhood eGFR were partly explained by childhood vitamin D status. CONCLUSIONS: Our findings suggest that maternal 25(OH)D levels during pregnancy may influence childhood kidney outcomes. These results should be considered hypothesis generating. Further studies are needed to replicate the observations, to examine the underlying mechanisms and to identify the long-term clinical consequences.