Background Early life factors may influence kidney growth and function throughout the life course. We examined the associations of breastfeeding duration and exclusivity and age at introduction of solid foods with kidney outcomes at school age. Study Design Prospective cohort study from fetal life onward. Setting & Participants 5,043 children in the Netherlands. Predictors Infant feeding was assessed prospectively using questionnaires. Outcomes & Measurements In children at a median age of 6.0 years, we measured kidney volume with ultrasound, estimated glomerular filtration rate (eGFR) from serum creatinine level, and microalbuminuria from urinary albumin and creatinine levels. Results 92% of all children were ever breastfed, of whom 27% were breastfed for more than 6 months and 21% were breastfed exclusively for at least 4 months. Compared with ever-breastfed children, never-breastfed children had smaller combined kidney volumes (-2.69 [95% CI, -4.83 to -0.56] cm<sup>3</sup>) and lower eGFRs (-2.42 [95% CI, -4.56 to -0.28] mL/min/1.73 m<sup>2</sup>) at school age. Among breastfed children, shorter duration of breastfeeding was associated with smaller combined kidney volume and lower microalbuminuria risk (P < 0.05). Compared to exclusive breastfeeding for 4 months, nonexclusive breastfeeding in the first 4 months was associated with smaller combined kidney volume and lower eGFR (both P < 0.05). Associations with eGFR were explained largely by kidney volume. Age at introduction of solid foods was not associated with any kidney outcome. Limitations Observational study, so causality cannot be established. Follow-up measurements were available for 76% of children. Conclusions These results suggest that breastfeeding is associated with subclinical changes in kidney outcomes in childhood. Further studies are needed to explore whether early life nutrition also affects the risk of kidney disease in adulthood.

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Keywords albumin-creatinine ratio (ACR), Breastfeeding, early-life nutrition, epidemiology, estimated glomerular filtration rate (eGFR), Generation R Study, infant diet, kidney development, kidney function, kidney growth, kidney volume, nephrogenesis, renal ultrasound
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Journal American Journal of Kidney Diseases
Miliku, K, Voortman, R.G, Bakker, H, Hofman, A, Franco, O.H, & Jaddoe, V.W.V. (2015). Infant Breastfeeding and Kidney Function in School-Aged Children. American Journal of Kidney Diseases, 66(3), 421–428. doi:10.1053/j.ajkd.2014.12.018