Fetal and Infant Growth Patterns and Kidney Function at School Age

Abstract

Low birth weight is associated with ESRD. To identify specific growth patterns in early life that may be related to kidney function in later life, we examined the associations of longitudinally measured fetal and infant growth with kidney function in school-aged children. This study was embedded in a populationbased prospective cohort study among 6482 children followed from fetal life onward. Fetal and childhood growth was measured during second and third trimesters of pregnancy, at birth, and at 6, 12, 24, 36, and 48 months postnatally. At the age of 6 years, we measured kidney volume by ultrasound. GFR was estimated using blood creatinine levels. Higher gestational age-adjusted birth weight was associated with higher combined kidney volume and higher eGFR (per 1 SD score increase in birth weight; 1.27 cm 3 [95% confidence interval, 0.61 to 1.93] and 0.78 ml/min per 1.73 m 2 [95% CI, 0.16 to 1.39], respectively). Fetal weight, birth weight, and weight at 6 months were positively associated with childhood kidney volume, whereas higher second trimester fetal weight was positively associated with higher GFR (all P values,0.05). Fetal and childhood lengths were not consistently associated with kidney function. In this cohort, lower fetal and early infant weight growth is associated with smaller kidney volume in childhood, whereas only lower fetal weight growth is associated with lower kidney function in childhood, independent of childhood growth. Whether these associations lead to an increased risk of kidney disease needs to be studied further.

The Life Cycle of the Kidney

“…7 Notably, higher second-trimester fetal weight was associated with higher childhood GFR, and higher birth weight was associated with higher kidney volume and GFR. 7 In the second study of 923 pregnant women and their children, fetal growth, kidney volume, and umbilical and cerebral artery blood flow were measured in the third trimester. 9 These were followed by measurement of BP, kidney volume, and GFR in childhood.…”

“…Compared with children with solitary kidney who were followed ,5 years, urinary microalbuminuria was significantly higher in those followed .5 years. 16 The significant association of fetal kidney volume with childhood kidney volume and eGFR in the study by Bakker et al 7 underscores the importance of renal mass as a determinant of renal function. Renal length increases at a rate of 3 mm per month at birth, decreases to 2 mm per month at 6 months, and then slows markedly to 0.25 mm per month thereafter.…”

“…Previous studies show that first-trimester fetal length smaller than expected for gestational age is associated with low birth weight and premature delivery. 10 This finding, along with the association of reduced fetal growth with decreased GFR in childhood, 7 suggests that early impairment of metanephric growth is a risk factor for reduced postnatal renal function.…”

“…In one study, fetal growth was measured by ultrasonography in the second and third trimesters, during which nephron number increases 50-fold. 7,8 These data were correlated with renal growth and eGFR through 6 years of age in 6482 children. 7 Notably, higher second-trimester fetal weight was associated with higher childhood GFR, and higher birth weight was associated with higher kidney volume and GFR.…”

“…7,8 These data were correlated with renal growth and eGFR through 6 years of age in 6482 children. 7 Notably, higher second-trimester fetal weight was associated with higher childhood GFR, and higher birth weight was associated with higher kidney volume and GFR. 7 In the second study of 923 pregnant women and their children, fetal growth, kidney volume, and umbilical and cerebral artery blood flow were measured in the third trimester.…”