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Table 2 Incidence of infant mortality and adjusted incidence rates of the determinants analyzed according to birth weight strata

From: The relationship between the different low birth weight strata of newborns with infant mortality and the influence of the main health determinants in the extreme south of Brazil

 Crude analysisAdjusted analysisCrude analysisAdjusted analysisCrude analysisAdjusted analysis
Mortality rate (%)PIR (CI 95%) adj*Mortality rate (%)PIR (CI 95%) adj*Mortality rate (%)PIR (CI 95%) adj*
 500–900 g1000–1499 g1500–2499 g
Biological determinants
Maternal age
 10–17 years66.670.01530.93 (0.81;1.07)19.670.00031.74 (1.15;2.65)2.190.01061.40 (0.94;2.08)
 ≥ 35 years42.370.00020.87 (0.74;1.02)7.440.05120.78 (0.53;1.16)1.480.8815 
 18–34 years56.79 110.79 11.44 1
Gender
 Male59.850.00061.16 (1.05;1.27)12.260.05631.29 (1.00;1.66)1.720.04661.07 (0.85;1.35)
 Female50.37 19.66 11.37 1
Gestational age
 < 22 weeks92.50< 0.00011.59 (1.29;1.96)+     
 22–27 weeks63.19< 0.00011.43 (1.23;1.66)23.18< 0.00011.90 (1.27;2.84)+  
 28–31 weeks35.60 111.240.00991.27 (0.93;1.73)5.03< 0.00013.06 (2.03;4.61)
 32–36 weeks+  7.48 11.620.00081.48 (1.13;1.94)
 ≥ 37 weeks+  +  1.05 1
5-min Apgar Index
 < 775.68< 0.00011.43 (1.29;1.59)28.46< 0.00012.90 (2.21;3.81)11.36< 0.00016.3 (4.61;8.71)
 ≥ 740.18 17.78 11.21 1
Skin color of the mother
 Black/Brown/Asian/Indigenous62.860.00061.02 (0.92;1.14)11.440.6284 1.820.07220.89 (0.68;1.18)
 White52.49 110.67  1.45 1
Social determinants
Maternal schooling
 None/< 8 years65.60< 0.00011.11 (0.94;1.32)15.070.00020.83 (0.55;1.25)2.32< 0.00011.65 (1.06;2.58)
 8–11 years54.700.00011.01 (0.86;1.19)9.080.3674 1.180.05981.12 (0.72;1.72)
 ≥ 12 years39.73 17.64 10.83 1
Previous living children
 151.050.7130 11.490.03201.41 (1.00;1.98)1.560.06201.26 (0.91;1.75)
 263.970.00601.13 (0.97;1.31)15.94< 0.00012.28 (1.55;3.35)1.670.05601.20(0.79;1.80)
 ≥ 365.340.00011.07 (0.91;1.25)15.00< 0.00011.72 (1.13;2.63)2.63< 0.00011.43 (0.97;2.11)
 Nenhum52.34 18.12 11.18 1
Previous deceased children
 ≥ 155.170.9570 7.800.08080.64 (0.40;1.03)1.930.13331.19 (0.82;1.71)
 None54.96 111.35 11.49 1
Health care determinants
Prenatal visits
 None76.79< 0.00011.03 (0.84;1.26)16.86< 0.00011.41 (0.84;2.37)3.40< 0.00012.38 (1.54;3.68)
 1–361.48< 0.00011.00 (0.82;1.21)14.79< 0.00011.65 (1.05;2.60)2.70< 0.00012.14 (1.47;3.12)
 4–648.00.00120.92 (0.75;1.13)10.950.00011.60 (1.02;2.49)1.59< 0.00011.49 (1.06;2.08)
 ≥ 734.55 14.82 10.85 1
Type of delivery
 Cesarean37.93< 0.00010.74 (0.66;0.84)8.44< 0.00010.75 (0.56;0.99)1.460.4301 
 Vaginal72.34 116.02 11.60  
Type of hospital
 Public65.86< 0.00011.85 (1.41;2.43)12.050.00041.56 (0.84;2.88)1.79< 0.00011.01 (0.62;1.64)
 Mixed47.66< 0.00011.46 (1.10;1.94)11.300.00151.45 (0.77;2.74)1.570.00150.81 (0.49;1.33)
 Private26.73 14.72 10.83 1
 2500–2999 g3000–3999 g≥ 4000 g
Biological determinants
Maternal age
 10–17 years0.580.4529 0.50< 0.00011.56 (1.13;2.14)0.300.9178 
 ≥ 35 years0.400.18210.72 (0.51;1.03)0.160.00230.63 (0.45;0.88)0.1550.2458 
 18–34 years0.50 10.26 10.28  
Gender
 Male0.550.08861.11 (0.89;1.39)0.300.00231.29 (1.07;1.57)0.240.5527 
 Female0.45 10.23 10.29  
Gestational age
 < 22 weeks+  +  +  
 22–27 weeks+  +  +  
 28–31 weeks+  +  +  
 32–36 weeks0.770.00021.48 (1.11;1.99)0.560.00051.55 (0.92;2.29)+  
 ≥ 37 weeks0.45 10.26 10.26  
5-min Apgar Index
 < 76.81< 0.000112.19 (8.44;17.61)6.06< 0.000122.28 (17.9;29.06)9.32< 0.000158.54 (28.67;119.50)
 ≥ 70.44 10.22 10.17 1
Skin color of the mother
 Black/Brown/Asian/Indigenous0.82< 0.00011.30 (1.02;1.67)0.43< 0.00011.28 (1.05;1.57)0.370.11621.53 (0.76;3.09)
 White0.40 10.22 10.21 1
Social determinants
Maternal schooling
 None/< 8 years0.91< 0.00011.58 (1.00;2.470.47< 0.00012.30 (1.53;3.46)0.420.02782.24 (0.62;8.02)
 8–11 years0.330.03780.88 (0.57;1.36)0.24< 0.00011.59 (1.07;2.35)0.230.32931.39 (0.44;4.37)
 ≥ 12 years0.22 10.10 10.14 1
Previous living children
 10.430.03401.35 (0.96;1.90)0.240.3070 0.250.2870 
 20.63< 0.00011.63 (1.09;2.45)0.310.00601.32 (0.96;1.81)0.450.02402.69 (1.07;6.79)
 ≥ 31.30< 0.00012.64 (1.82;3.81)0.52< 0.00011.65 (1.21;2.24)0.340.10401.16 (0.41;3.31)
 Nenhum0.31 10.21 10.15  
Previous deceased children
 ≥ 10.590.2986 0.330.13621.16 (0.84;1.59)0.220.7627 
 None0.49  0.26 10.26  
Health care determinants
Prenatal visits
 None1.81< 0.00012.90 (2.01;4.19)1.17< 0.00013.79 (2.70;5.33)1.82< 0.00016.97 (2.24;21.70)
 1–31.03< 0.00011.76 (1.26;2.45)0.52< 0.00011.81 (1.34;2.45)0.540.04041.98 (0.61;6.44)
 4–60.56< 0.00011.19 (0.88;1.59)0.35< 0.00011.36 (1.07;1.73)0.220.7916 
 ≥ 70.30 10.19 10.20 1
Type of delivery
 Cesarean0.380.00040.96 (0.74;1.25)0.240.03051.39 (1.13;1.70)0.300.2895 
 Vaginal0.58 10.29 10.21  
Type of Hospital
 Public0.53< 0.00011.30 (0.79;2.15)0.31< 0.00011.41 (0.93;2.13)0.330.09321.16 (0.38;3.51)
 Mixed0.73< 0.00011.69 (1.02;2.79)0.35< 0.00011.60 (1.05;2.43)0.210.4613 
 Private0.17 10.11 10.13 1
  1. *Adjusted model to variables of the same stratum with P < 0.20 in the bivariate analysis. IR, incidence ratio; CI 95%, confidence interval of 95% no population