MATURITY VERSUS WEIGHT AS PREDICTORS OF SYSTOLIC BLOOD PRESSURE (SBP) IN LOW BIRTHWEIGHT (LBW) INFANTS DURING THE 1st SIX WEEKS (WKS) OF LIFE

Abstract

Although research in SBP in newborns suggests that chronological age (CA) and gestational age (GA) may be predictors of SBP, weight (WT) is more commonly used to evaluate SBP in LBW infants. This study was designed to determine the contribution of WT versus CA, GA and postconceptual age (PCA=GA+CA) to SBP in LBW infants (birthweight BW≤1500 gm) over the 1st wks of life. The SBP of 33 symptomatic infants (BW=1071±242 gm, GA=29.1±1.9 wks) was determined daily for the 1st 6 wks of life using a Dinamap monitor. Three maturity effects of SBP were noted: GA at birth, CA during the 1st wk and PCA during wks 2-6. At birth GA, BW and SBP were highly correlated: GA/BW (.75), GA/SBP (.50), BW/SBP (.33). Regression analysis (RA) revealed that at birth GA made an independent contribution (IC) of 16%, GA/WT overlapped to predict 9%, BW made no IC to SBP. SBP during the 1st wk of life was correlated with CA (.49), GA(.41), WT (.20). RA revealed that the independent contributors to SBP during the 1st week of life were CA 24%, GA 7%, WT 0%. The overlap between GA/WT contributed 10% of the variance. During wks 2-6 PCA was the most important predictor of SBP. PCA/SBP were correlated (.40); PCA made an IC of 5% of the variance in SBP and combined to predict an additional 11% of the variance during wks 2-6 (multiple R=.40). This study suggests that the common practice of using WT to evaluate SBP in LBW infants ignores the majority of systematic variance available from each of the three operations of maturity: GA, CA and PCA.