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Table 5 Crude and adjusted odds ratios of preterm birth a associated with mothers’ socio demographic characteristics

From: Sociodemographic characteristics of mother’s population and risk of preterm birth in Chile

Periods 1991-1995 1996-2000 2001-2008
Mothers’ characteristicsb Crude OR CI [95%] Adjusted ORc CI [95%]c Crude OR CI [95%] Adjusted OR CI [95%] Crude OR CI [95%] Adjusted OR CI [95%]
Age <18 1.42 [1.38,1.47] 1.26 [1.22,1.30] 1.33 [1.29,1.37] 1.24 [1.21,1.28] 1.28 [1.25,1.31] 1.20 [1.17,1.23]
18-38   1.0 Referenced    1.0 Reference    1.0 Reference  
>38 1.76 [1.69,1.82] 1.78 [1.72,1.85] 1.76 [1.70,1.82] 1.82 [1.75,1.88] 1.59 [1.56,1.63] 1.65 [1.61,1.69]
Marital Status Living with a partner   1.0 Reference    1.0 Reference    1.0 Reference  
Not living with a partner 1.20 [1.18,1.22] 1.16 [1.14,1.18] 1.06 [1.04,1.08] 1.02 [1.00,1.04] 1.03 [1.02,1.04] 1.17 [1.14,1.20]
Parity Primiparous 1.09 [1.08,1.12] 1.07 [1.05,1.09] 1.10 [1.08,1.12] 1.11 [1.09,1.13] 1.10 [1.09,1.12] 1.12 [1.11,1.14]
Multipara   1.0 Reference    1.0 Reference    1.0 Reference  
Grand multipara 1.38 [1.31,1.46] 1.33 [1.25,1.42] 1.30 [1.22,1.38] 1.28 [1.19,1.38] 1.30 [1.23,1.37] 1.26 [1.18,1.35]
  1. Chile, Singletons live births, 1991–2008.
  2. aPreterm births : < 37 weeks of gestational age.
  3. bReference classes: 18–38 years, living with partner, multipara.
  4. cAll adjusted OR ( for the others factors in table) with P < 0.001 for Wald’s chi-square.