Creatinine at Birth Correlates with Gestational Age and Birth Weight: Another Factor of the Imbroglio in Early Neonatal Life

Abstract

<b><i>Background:</i></b> Serum creatinine (S<sub>cr</sub>) in early neonatal life (first week of life) displays extensive variability; hence, a better understanding is needed to use S<sub>cr</sub> as a diagnostic biomarker for acute kidney injury (AKI). <b><i>Objective:</i></b> The objective of this study was to explore S<sub>cr</sub> trends and its covariates in early neonatal life. <b><i>Methods:</i></b> Analysis of a rich, pooled S<sub>cr</sub> dataset (enzymatic assay) of 4,509 S<sub>cr</sub> observations in 1,181 neonates in the first week of life with birth weight, gestational age (GA), and postnatal age as covariates was conducted. Descriptive data were summarized as median and range. The Spearman rank correlation test was used to examine S<sub>cr</sub>, while the Mann-Whitney U test was used to determine the differences between the different GA (≤32, 33–36, or ≥37 weeks) categories. <b><i>Results:</i></b> The median S<sub>cr</sub> at delivery was 55.7 (range 28.3–194.5) µmol/L, correlating with birth weight (<i>r</i> = 0.088) or GA (<i>r</i> = 0.183) for the full dataset. At birth, the median S<sub>cr</sub> was highest in term (≥37-week) neonates. In early neonatal life (median S<sub>cr</sub> values), there was a gradual increase to attain a peak S<sub>cr</sub> by day 2–3, highest and most delayed in neonates ≤32 weeks GA. This is followed by a blunted decrease when ≤32-week neonates were compared to those of 33–36 or ≥37 weeks GA. <b><i>Conclusions:</i></b> The S<sub>cr</sub> pattern in early neonatal life is complex, with the highest S<sub>cr</sub> at birth in full-term neonates, while those ≤32 weeks GA displayed the highest and delayed peak S<sub>cr</sub> with a subsequent blunted decrease. Knowledge of these patterns is crucial to explore the utility of S<sub>cr</sub> as an AKI biomarker.

Creatinine Trends and Patterns in Neonates Undergoing Whole Body Hypothermia: A Systematic Review

“…In both data sets, we noticed a similar pattern with an initial increase from birth onwards over the first day of postnatal life and a subsequent decline after the first day of postnatal life, confirming the patterns earlier described in other cohorts of (near)term neonates [52][53][54].…”

Quantification of Fetal Renal Function Using Fetal Urine Production Rate and Its Reflection on the Amniotic and Fetal Creatinine Levels During Pregnancy

“… Creatinine level in the amniotic and fetal fluids. (A) Fetal amniotic creatinine concentration as a function of fetal age, (B) weighted means (circles) and SD of amniotic creatinine level plotted against Fetal age, (C) Amniotic creatinine concentration against predicted FUPR based on the function derived from 3D data (D) reported references values for the creatinine in fetal urine from fetuses diagnosed with ( 6 , 48 ) and without ( 49 ) urinary tract uropathies (E) Fetal amniotic to urine creatinine ratio, and (F) Serum creatinine in maternal serum [lines ( 50 )] overlaying measured neonatal serum creatinine at birth [squares ( 51 )]. Solid and broken lines represent the median and 5th-95th intervals.…”

“…Data were generated using this function assuming 25% CV and then compared against 4,509 SerCr measurements obtained at birth (23–42 GAs) from 1,181 newborns ( 51 ). Due to its low molecular weight (113.12 g/mol), creatinine freely passes the placental barrier and its level at birth is known to reflect the maternal level.…”

“…In the current work, since fetal SerCr is a required parameter for the fetal GFR calculation, (see Method section), we have compared the maternal SerCr using a previously developed gestational age-dependent maternal SerCr function ( 50 ) with neonatal SerCr obtained at birth from 1,181 newborns between 23 and 42 GAs ( 51 ) to assess any trend. As shown in Figure 3F , the neonatal data were almost identical to the maternal SerCr at different weeks of pregnancy, therefore the maternal data was used, rather than the neonatal data since the original function was derived from observed data during the different trimesters, while extrapolating the neonatal data to GAs earlier than 24 GAs is questionable.…”

Metabolomics Applied to Cord Serum in Preeclampsia Newborns: Implications for Neonatal Outcomes

“…Creatinine and uric acid were generally considered to be associated with kidney function. It was reported that neonatal creatinine could reflects the level of maternal renal function ( 26 ), and predict the onset of neonatal acute kidney injury to some extent ( 27 ). Uric acid have effects on fetal growth and kidney development, and lead to a tendency of low-birth-weight infants ( 28 ).…”