The relationship between low birth weight (LBW) and subsequent increased risk of hypertension and renal disease in humans is now well established. The initial hypothesis suggested that an adverse intrauterine environment, reflected by LBW, would impact renal development, resulting in a low nephron number and predisposition to hypertension and renal disease. Studies in various populations have shown a direct correlation between birth weight and nephron number, and in infants, nephron numbers are reduced in those of LBW. Among Caucasian and Australian Aboriginal adults, lower nephron numbers are associated with higher blood pressure, whereas higher nephron numbers appear to protect against hypertension. LBW is currently the best clinical surrogate for low nephron number and has been independently associated with higher blood pressure from infancy through to adulthood in many populations, as well as an increased risk of proteinuria, reduced glomerular filtration rate, chronic kidney disease, and end-stage renal disease in later life. The pathophysiology is analogous to that in other chronic kidney diseases where surviving nephrons are subject to hyperfiltration early on, resulting in glomerular hypertrophy, proteinuria, and eventually, especially in the setting of other renal disease risk factors, glomerulosclerosis, and loss of renal function.
Mean nephron number varies by up to 13-fold in certain populations, however, therefore nephron number is unlikely the sole developmentally programmed risk factor for renal disease in later life, but may be a first ‘hit’ impacting an individual’s susceptibility to or resistance to superimposed renal injury. Augmentation of nephron number perinatally has only been addressed in experimental settings.
In humans, therefore optimization of nephron number is likely best achieved through good perinatal care and adequate postnatal nutrition. Cardiovascular disease and diabetes are also developmentally programmed and therefore likely coexist in subjects with LBW and low nephron numbers. Awareness of an individual’s birth weight should serve to highlight the possibility of low nephron number and potential risk for future hypertension and renal disease, which may be attenuated by optimization of early nutrition, lifestyle choices, and management of other risk factors for renal disease.
Low Birth Weight and Risk of Progression to End Stage Renal Disease in IgA Nephropathy—A Retrospective Registry-Based Cohort Study
