POSTCONCEPTUAL AGE (PCA) AS A BASIS FOR SYSTOLIC BLOOD PRESSURE (SBP) NORMS IN LOW BIRTHWEIGHT (LBW) INFANTS

Abstract

Chronological age (CA) and gestational age (GA) are often used to predict newborn SBP. The purpose of this study was to test the contribution of PCA (PCA=CA+GA) to SBP and to use PCA as a basis for SBP norms in LBW infants. 33 LBW infants (BW=1071±242, GA=29.1 ±1.9 wks) were studied with daily Dinamap SBP determinations to a CA=6-8 wks. Infants were grouped by GA: (1)25-27 wks (n=8); (2)28-29 wks (n=10); (3)30-32 wks (n=15). At birth SBP was: Grp 1=50.7±7.0, Grp 2=54.0±8.0, Grp 3=56.6±8.0. SBP increased significantly in each grp during wk 1 (CA effect). SBP rose differentially in the 3 grps after wk 1 of life; PCA predicted the time required to reach term newborn SBP levels. The SBP of grp 3 plateaued after wk 1 at 68.1±6.3; the SBP of grp 2 rose wks 1-2 (p <.001) and wks 2-5 (p<.03), plateauing after wk 5 at 69.8±6.4. Grp 1 SBP rose wks 1-2 (p<.06) and wks 2-7 (p<.01); SBP at wk 7= 68.8±7.3. The mean PCA of all GA grps upon achieving the SBP plateau was 32-33 wks. Achievement of term SBP levels at a similar PCA and differing CA supports the construct validity of PCA as a predictor of SBP. SBP norms by PCA with the Dinamap method (after the wk 1 CA effect) are:

These data document an initial CA effect in all GA groups and the continued rise in SBP to a PCA of 32-33 weeks.

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