Kidney growth in small-for-gestational-age infants: evidence of early accelerated renal growth

Abstract

Background. Very few data are available on longitudinal renal growth in small for gestational age (SGA) infants born at term. The aim of this prospective study was to estimate comparatively the renal growth in SGA infants and in infants born appropriate for gestational age (AGA) during the first 2 years of life. Methods. The study comprised groups of SGA and AGA infants with a gestational age (GA) of 36-41 weeks. The SGA group was classified into two subgroups of symmetrical and asymmetrical neonates according to the ponderal index. Serial renal ultrasonography (US) was performed at the ages of 41 weeks corrected age [GA (in weeks) plus age after birth (in weeks)] and at 3, 6, 12 and 24 months of chronological age and kidney length (KL) was related to other anthropometric indices. Results. A total of 312 infants participated in the study out of which 197 were SGA, and a total number of 802 measurements were performed. The symmetrical SGA infants and, to a lesser degree, the asymmetrical SGA infants had smaller kidneys at birth compared with the AGA infants (P < 0.0001 and P < 0.001, respectively). The symmetrical SGA infants had a lower body weight (BW) (P < 0.001, P < 0.01) and crown-heel length (CHL) (P < 0.01, P < 0.05) than controls at the ages of 12 and 24 months of chronological age. The asymmetrical SGA infants had a lower BW (P < 0.01, P < 0.05) than controls at the ages of 12 and 24 months of chronological age. On the contrary, the KL in both SGA groups was not different from that of the AGA infants after the 41st week of corrected age and up to the 2nd year of life. Conclusion. SGA term infants had shorter KL at birth compared with AGA infants but a similar length from the 3rd to the 24th month of life. Early catch-up kidney growth was observed in both SGA groups and is more prominent in the symmetrical SGA infants. This observation may represent either an accelerated renal maturation process or early compensatory kidney hypertrophy in this group of infants.

The Effect of Prepregnancy Body Mass Index and Gestational Weight Gain on Birth Weight

“…They reported that SGA infants had shorter kidney length at birth compared with AGA infants. Similar findings were observed in the SGA term infant, but the association disappeared in later childhood (Giapros et al, 2006).…”

The Kidney from Prenatal to Adult Life: Perinatal Programming and Reduction of Number of Nephrons during Development

“…At a later stage of life the same animals developed high arterial blood pressure featuring glomerular hypertrophy and hyperfiltration of kidneys manifested as a compensatory mechanism for the reduced number of nephrons [5]. In spite of the finding in humans that small for gestational age (SGA) newborns displayed shorter renal length than appropriate for gestational age (AGA), on ageing they manifested either an accelerated renal maturation process or early compensatory kidney hypertrophy [6]. A low nephron endowment led to the onset of compensatory mechanisms in the residual nephrons consisting of glomerular hypertension, high nephron filtration rates, and lastly glomerular hypertrophy [7].…”

Renal function and kidney length in preterm infants with nephrocalcinosis: a longitudinal study

“…SGA infants have lower nephron numbers at birth than those born AGA, and SGA and extremely preterm infants may also have lower KL during the first 2 years of life [23,30]. NC might further affect the early renal development in this group.…”

“…Differences were considered to be significant at p<0.05. The number of infants included in the study was selected to allow a minimum of 60 measurements for each comparison in any study period, after taking into account the drop-off trends in previous studies of similar design in this centre [23]. This number of infants was considered to be sufficient to document a 15% difference in serum and renal parameters and KL between the groups with a power of>0.80 at a significance level of p<0.05 [24].…”