Birth weight - A risk factor for progression in diabetic nephropathy?

Objectives. Intrauterine growth retardation, as seen in individuals with low weight at birth, may give rise to a reduction in nephron number. Oligonephropathy has been linked to hypertension and renal disease in adult life. We tested the concept that low weight at birth acts as a risk factor for progression of diabetic nephropathy. Design and subjects. We performed an observational follow-up study of 161 (97 men) type 1 diabetic patients with diabetic nephropathy [mean age (SD): 35 (11) years, mean duration of diabetes: 22 (8) years]. All patients had been followed for at least 3 years [median (range): 8 (3-20)] with at least three measurements [9 (3-31)] of glomerular filtration rate (GFR) (⁵¹Cr-EDTA). Information about birth size was obtained from midwife registrations. Settings. Steno Diabetes Center, a tertiary referral centre. Main outcome measures. Loss of kidney function according to birth weight and weight/length ratio at birth. Results. There was no correlation in univariate analysis between birth weight or weight/length ratio and rate of decline in GFR, neither in men nor in women. Furthermore, the 27 patients with birth weights below the 20th centile had a rate of decline in GFR [median (range)] similar to the 134 patients above: 2.6 (-4.7; 9.6) vs, 3.4 (-2.3; 19.3) mL min^-1 year^-1, respectively (NS). A multiple regression analysis revealed that albuminuria, arterial blood pressure, and haemoglobin A_1C during follow-up showed a significant correlation with the decline in GFR [R² (adjusted) = 0.34], whereas birth weight and birth weight/length ratio did not. Conclusions. Our study does not suggest that weight at birth is associated with progression of established diabetic nephropathy in type 1 diabetic patients, whilst several other potential modifiable risk factors were identified.