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Table 3 ORs (95%CI) for the adverse pregnancy outcomes according to the quartiles of urea nitrogen (UN)

From: Serum urea acid and urea nitrogen levels are risk factors for maternal and fetal outcomes of pregnancy: a retrospective cohort study

  UN (mmol/L) in the second trimester Ptrend Per–SD increase
Q1 (< 2.23) Q2 (2.23–2.50) Q3 (2.55–3.00) Q4 (> 3.00)
PROM
 Case/N 88/458 76/352 80/442 69/350   
 Model 1 1 (ref) 1.16 (0.82, 1.63) 0.93 (0.66, 1.30) 1.03 (0.73, 1.47) 0.838 0.97 (0.86, 1.10)
 Model 2 1 (ref) 1.15(0.82, 1.63) 0.95(0.68, 1.34) 1.05(0.73, 1.50) 0.938 0.98(0.86, 1.11)
PTB
 Case/N 9/458 7/352 12/442 9/350   
 Model 1 1 (ref) 1.01 (0.37, 2.75) 1.39 (0.58, 3.34) 1.32 (0.52, 3.35) 0.440 1.02 (0.73, 1.40)
 Model 2 1 (ref) 0.98 (0.35, 2.71) 1.36 (0.56, 3.32) 1.26 (0.48, 3.28) 0.500 0.98 (0.71, 1.37)
LBW
 Case/N 8/458 4/352 8/442 9/350   
 Model 1 1 (ref) 0.65 (0.19, 2.17) 1.04 (0.39, 2.79) 1.49 (0.58, 3.89) 0.349 1.10 (0.77, 1.56)
 Model 2 1 (ref) 0.75(0.22, 2.58) 1.03(0.38, 2.85) 1.58(0.58, 4.29) 0.346 1.12(0.78, 1.61)
SGA
 Case/N 18/458 12/352 27/442 26/350   
 Model 1 1 (ref) 0.86 (0.41, 1.82) 1.59 (0.86, 2.93) 1.96 (1.06, 3.64) 0.011 1.18 (0.96, 1.46)
 Model 2 1 (ref) 0.90(0.43, 1.92) 1.54(0.83, 2.87) 2.18 (1.16, 4.13) 0.007 1.21(0.98, 1.50)
  UN (mmol/L) in the third trimester   
Q1 (< 2.45) Q2 (2.45–2.90) Q3 (2.93–3.35) Q4 (> 3.35)
PROM
 Case/N 87/408 85/455 55/339 86/400   
 Model 1 1 (ref) 0.85 (0.61, 1.18) 0.72 (0.49, 1.04) 1.01 (0.72, 1.41) 0.874 1.01 (0.89, 1.14)
 Model 2 1 (ref) 0.83 (0.59, 1.16) 0.65 (0.44, 0.96) 0.91 (0.65, 1.29) 0.443 0.97 (0.85, 1.10)
PTB
 Case/N 14/408 8/455 6/339 9/400   
 Model 1 1 (ref) 0.50 (0.21, 1.21) 0.51 (0.19, 1.33) 0.65 (0.28, 1.51) 0.309 0.74 (0.52, 1.06)
 Model 2 1 (ref) 0.50 (0.21, 1.22) 0.49 (0.18, 1.33) 0.68 (0.28, 1.60) 0.354 0.75 (0.52, 1.08)
LBW
 Case/N 8/408 8/455 4/339 9/400   
 Model 1 1 (ref) 0.89 (0.33, 2.41) 0.60 (0.18, 2.00) 1.15 (0.44, 3.01) 0.898 1.01 (0.69, 1.45)
 Model 2 1 (ref) 0.82 (0.30, 2.27) 0.54 (0.15, 1.87) 1.06 (0.39, 2.86) 0.996 0.99 (0.68, 1.44)
SGA
 Case/N 15/408 16/455 20/339 32/400   
 Model 1 1 (ref) 0.96 (0.47, 1.96) 1.64 (0.83, 3.26) 2.28 (1.21, 4.28) 0.002 1.38 (1.13, 1.68)
 Model 2 1 (ref) 0.86 (0.42, 1.79) 1.57 (0.78, 3.16) 2.29 (1.20, 4.36) 0.002 1.35 (1.11,1.64)
  1. PROM premature rupture of membranes, PTB premature birth, LBW low birth weight infants, SGA small for gestational age infants. Model 1: without adjustment. Model 2: adjustment for age, pre–pregnancy BMI, education, smoking status, alcohol status, conception method, number of pregnancies, parity, history of miscarriage, gestational diabetes mellitus and gestational hypertension