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Table 2 List of variables analysed using Artificial Neural Networks (ANNS) and their linear correlation index (r2) with each target variable.

From: Placental determinants of fetal growth: identification of key factors in the insulin-like growth factor and cytokine systems using artificial neural networks

  Variables Correlation index (r2)
1 Chronological age of the mother at delivery (years) 0,11
2 Sex of the newborn 0
3 Gestational age (weeks) 0,22
4 Other siblings (yes or No) 0,001
5 Number of other siblings 0,005
6 Number of previous abortions 0,000
7 Total placental protein content in lysates (mg/ml) 0,007
8 IGF-II concentration in placental lysates (ng/mg) 0,16
9 IGFBP-2 concentration in placental lysates (ng/mg) 0,05
10 IL-6 concentration in placental lysates (pg/mg) 0,09
11 TNF-α concentration in placental lysates (ng/mg) 0,05
12 IGF-I relative gene expression in placenta (A.U./18S, UBQ) 0,01
13 IGF-II relative gene expression in placenta (A.U./18S, UBQ) 0,02
14 IGFBP-1 relative gene expression in placenta (A.U./18S, UBQ) 0,05
15 IGFBP-2 relative gene expression in placenta (A.U./18S, UBQ) 0,08
16 IL-6 relative gene expression in placenta (A.U./18S, UBQ) 0,16
  1. Biochemical data were measured as specified in materials and methods. Gene expressions are in arbitrary units (AU) with respect to two house-keeping genes, 18 S ribosomal RNA (18S) and ubiquitin (UBQ). Specific protein concentrations in placental lysates are ng or pg per mg of placenta.