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17: Customized growth curves better identify fetal growth restriction and short term neonatal outcomes in preterm low birth weight infants

      Objective

      Compare body fat percent (BF%) and neonatal outcomes of preterm small for gestational age (SGA) infants based on customized (SGAcust) versus population (SGApop) growth curves.

      Study Design

      This was an observational study of 204 preterm low birthweight (<2500 g) infants. Using population-based Fenton growth curves and customized Centile Calculator-Gestation Related Optimal Weight software by Gardosi, infants were classified as SGA (weight< 10th percentile) or appropriate for gestational age (AGA). Air-displacement plethysmography (PEA POD, Life Measurement, Inc, Concord, CA) was performed at a mean adjusted gestational age of 43.0 ± 10.4 weeks to determine BF%. Neonatal outcomes, hospital length of stay (LOS) and BF% were compared using analysis of variance, Student's t-test, Chi-square and logistic regression between SGA and AGA defined by the different growth curves.

      Results

      Population-based curves identified 47 SGA infants with mean BF% of 14.6 ± 6.7% compared to 15.2 ± 6.2% for the 157 AGA infants (p=0.53). Customized curves identified 109 SGA infants with a mean BF% of 14.1 ± 6.3% compared to 16.2 ± 6% for the 95 AGA infants (p=0.02). When both SGAcust and SGApop were included together in a multivariable model predicting BF%, SGAcust remained a significant predictor (p=0.02) whereas SGApop was not shown to be a significant independent predictor (p=0.50). RDS was significantly less in both SGA groups compared to AGA groups (SGApop OR = 0.43, CI [0.2-0.9]; SGAcust OR = 0.29, CI [0.1-0.6]) but was no longer significant after controlling for gestational age. LOS was not significantly different between SGApop and AGApop (p=0.78), but LOS was significantly different between SGAcust (40.9 ± 26.3 days) and AGAcust (48.9 ± 27.5 days; p=0.03).

      Conclusions

      Customized growth curves reclassified 30% of the preterm, low birthweight infants from AGA to SGA compared to a commonly used population-based growth curve developed for preterm infants. Customized growth curves better identified low infant BF%, neonatal morbidity risk, and LOS.
      Tabled 1
      GroupNBF%Birthweight (grams)Gestational age (weeks)RDS (%)LOS (days)
      SGApop4714.6 ± 6.7995 ± 35930.4 ± 2.863.843.7 ± 23.9
      AGApop15715.2 ± 6.21287 ± 51429.2 ± 3.380.344.9 ± 28.1
      SGAcust10914.1 ± 6.31169 ± 45830.4 ± 3.067.040.9 ± 26.3
      AGAcust9516.2 ± 6.31277 ± 53528.4 ± 3.287.448.9 ± 27.5