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Table 4 Association of ambient temperature at conception/delivery with birth weight in Brisbane, 2000-2010 (n=237,585)

From: Exploring associations of maternal exposure to ambient temperature with duration of gestation and birth weight: a prospective study

  Birth weight, kg
Crude Adjusted
Model 1 Model 2 Model 3a/b
β (95% CI) P value β (95% CI) P value β (95% CI) P value β (95% CI) P value
In the first week
 Maximum temperature
  >30 0.010 (0.002, 0.017) 0.016 0.010 (0.004, 0.016) 0.001 0.005 (-0.004, 0.013) 0.265 0.004 (-0.006, 0.013) 0.447a
  25-30 0.011 (0.006, 0.016) <.001 0.011 (0.007, 0.015) <.001 0.005 (-0001, 0.011) 0.084 0.005 (-0.001, 0.011) 0.130a
  20-25 Ref   Ref   Ref   Ref  
  ≤20 0.010 (-0.004, 0.025) 0.165 0.004 (-0.007, 0.015) 0.473 0.004 (-0.010, 0.016) 0.490 0.003 (-0.009, 0.015) 0.606a
 Minimum temperature
  >20 0.016 (0.009, 0.022) <.001 0.011 (0.006, 0.016) <.001 0.008 (0.001, 0.017) 0.048 0.006 (-0.004, 0.016) 0.215a
  15-20 0.006 (0.001, 0.012) 0.033 0.006 (0.002, 0.011) 0.004 0.002 (-0.003, 0.008) 0.417 0.002 (-0.005, 0.008) 0.587a
  10-15 Ref   Ref   Ref   Ref  
  ≤10 0.005 (-0.003, 0.013) 0.198 -0.001 (-0.007, 0.005) 0.761 0.002 (-0.004, 0.008) 0.550 0.002 (-0.005, 0.008) 0.601a
In the first four weeks
 Maximum temperature
  >30 0.010 (0.002, 0.018) 0.020 0.012 (0.006, 0.019) <.001 0.004 (-0.006, 0.014) 0.446 0.001 (-0.011, 0.011) 0.964a
  25-30 0.008 (0.003, 0.013) 0.002 0.009 (0.006, 0.013) <.001 0.001 (-0.006, 0.007) 0.947 -0.001 (-0.008, 0.006) 0.826a
  20-25 Ref   Ref   Ref   Ref  
  ≤20 0.010 (-0.017, 0.038) 0.472 0.005 (-0.016, 0.027) 0.642 0.005 (-0.016, 0.027) 0.645 0.003 (-0.020, 0.025) 0.822a
 Minimum temperature
  >20 0.018 (0.012, 0.024) <.001 0.011 (0.006, 0.016) <.001 0.006 (-0.003, 0.015) 0.190 0.001 (-0.011, 0.012) 0.962a
  15-20 0.006 (0.001, 0.011) 0.049 0.007 (0.003, 0.011) 0.002 0.001 (-0.005, 0.008) 0.719 -0.001 (-0.008, 0.007) 0.901a
  10-15 Ref   Ref   Ref   Ref  
  ≤10 0.008 (-0.001, 0.016) 0.057 -0.004 (-0.010, 0.003) 0.245 0.000 (-0.007, 0.007) 0.989 0.000 (-0.008, 0.008) 0.998a
In the last week
 Maximum temperature
  >30 Ref   Ref   Ref   Ref  
  25-30 0.015 (0.007, 0.022) <.001 0.010 (0.004, 0.016) <.001 0.008 (0.002, 0.014) 0.014 0.006 (0.000, 0.013) 0.066b
  20-25 0.015 (0.008, 0.023) <.001 0.014 (0.008, 0.020) <.001 0.008 (-0.001, 0.017) 0.078 0.011 (0.008, 0.018) 0.041 b
  ≤20 0.025 (0.009, 0.041) 0.002 0.025 (0.013, 0.037) <.001 0.016 (0.002, 0.030) 0.030 0.018 (0.010, 0.031) 0.024 b
 Minimum temperature
  >20 Ref   Ref   Ref   Ref  
  15-20 0.011 (0.005, 0.017) <.001 0.004 (-0.001, 0.008) 0.141 0.002 (-0.003, 0.007) 0.488 -0.001 (-0.006, 0.006) 0.935b
  10-15 0.012 (0.005, 0.018) <.001 0.009 (0.004, 0.014) <.001 0.004 (-0.005, 0.013) 0.352 0.002 (-0.008, 0.011) 0.723b
  ≤10 0.015 (0.007, 0.024) <.001 0.012 (0.005, 0.018) <.001 0.005 (-0.007, 0.017) 0.396 0.004 (-0.008, 0.016) 0.510b
In the last four weeks
 Maximum temperature
  >30 Ref   Ref   Ref   Ref  
  25-30 0.008 (-0.001, 0.016) 0.070 0.007 (0.001, 0.013) 0.038 0.005 (-0.002, 0.012) 0.145 0.003 (-0.004, 0.011) 0.349b
  20-25 0.014 (0.006, 0.023) <.001 0.016 (0.010, 0.023) <.001 0.016 (0.006, 0.026) 0.002 0.013 (0.002, 0.024) 0.021 b
  ≤20 0.004 (-0.024, 0.033) 0.774 0.012 (-0.011, 0.034) 0.411 0.007 (-0.016, 0.031) 0.544 0.008 (-0.016, 0.033) 0.527b
 Minimum temperature
  >20 Ref   Ref   Ref   Ref  
  15-20 0.011 (0.005, 0.017) <.001 0.005 (0.001, 0.010) 0.033 0.004 (-0.002, 0.009) 0.177 0.001 (-0.005, 0.008) 0.703b
  10-15 0.014 (0.007, 0.020) <.001 0.013 (0.008, 0.018) <.001 0.011 (0.001, 0.020) 0.029 0.005 (-0.006, 0.016) 0.363b
  ≤10 0.014 (0.005, 0.023) 0.003 0.013 (0.006, 0.020) <.001 0.010 (-0.002, 0.023) 0.113 0.003 (-0.012, 0.018) 0.681b
  1. Model 1: adjusted for maternal age at delivery, indigenous status, maternal marital status, mode of labor onset, parity, baby’s gender, and duration of gestation
  2. Model 2: further adjusted for relative humidity and air pressure around conception and delivery, along with all air pollutants (PM10, O3, NO2, and SO2) around conception and delivery
  3. Model 3a: model 2 adjustment plus calendar month at delivery, as well as maximum temperature and minimum temperature around delivery
  4. Model 3b: model 2 adjustment plus calendar month at delivery, as well as maximum temperature and minimum temperature around conception