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Table 4 Weight z--scores and percent of infants weighting less than the 10th percentile*

From: Validating the weight gain of preterm infants between the reference growth curve of the fetus and the term infant

  All infants 23 to 25 wks 26 to 28 weeks 29 to 31 weeks
Birth vs. FIGR-2013 [21]
median −0.1 0.1 0.1 −0.9
Average −0.2 0.0 0.0 −0.9
Standard deviation 0.8 0.8 0.8 0.6
Count 978 225 541 212
% less than 10th percentile 11% 6% 7% 26%
2 weeks postnatal age vs. FIGR-2013
median −1.0 −0.8 −0.8 −1.6
Average −1.0 −0.8 −0.8 −1.6
Standard deviation 0.6 0.6 0.6 0.6
Count 862 193 485 184
% less than 10th percentile 31% 22% 20% 68%
37 weeks gestational age vs. FIGR-2013
median −1.7 −1.9 −1.5 −2.1
Average −1.7 −1.9 −1.6 −2.1
Standard deviation 0.9 1.0 1.0 1.0
Count 696 169 382 145
% less than 10th percentile 65% 75% 60% 78%
40 weeks gestational age vs. FIGR-2013
median −1.6 −1.8 −1.3 −1.9
Average 1.3 1.3 1.3 1.2
Standard deviation −1.5 −1.7 −1.3 −1.8
Count 584 144 316 124
% less than 10th percentile 55% 63% 49% 62%
40 weeks gestational age vs. WHO Growth Standard [16]
median −0.9 −1.1 −0.7 −1.2
Average 1.1 1.2 1.1 1.1
Standard deviation −0.8 −1.0 −0.6 −1.1
Count 584 144 315 124
% less than 10th percentile 35% 39% 28% 47%
50 weeks post-menstrual age vs. WHO Growth Standard
median −1.1 −1.2 −1.0 −1.2
Average −1.2 −1.3 −1.1 −1.3
Standard deviation 1.2 1.1 1.2 1.0
Count 461 103 256 102
% less than 10th percentile 43% 48% 41% 45%
  1. *Z-scores and assessment of growth restriction (i.e. size less than the 10th percentile) were assigned relative to the fetal-infant growth reference (FIGR)-2013 of intrauterine measures for up to 40 weeks, the World Health Organization (WHO) Growth Standard was used for 40 and 50 weeks.