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Table 3 Association of ambient temperature at conception/delivery with duration of gestation 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

  Duration of gestation, weeks
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 Ref   Ref   Ref   Ref  
  25-30 0.008 (-0.017, 0.033) 0.539 0.003 (-0.016, 0.021) 0.791 -0.005 (-0.025, 0.015) 0.598 0.000 (-0.020. 0.021) 0.982a
  20-25 0.007 (-0.018, 0.033) 0.572 0.023 (0.004, 0.043) 0.021 -0.006 (-0.034, 0.021) 0.664 0.009 (-0.021, 0.038) 0.571a
  ≤20 0.026 (-0.026, 0.079) 0.322 0.031 (-0.009, 0.070) 0.135 -0.004 (-0.050, 0.041) 0.854 0.006 (-0.041, 0.052) 0.814a
 Minimum temperature
  >20 0.026 (0.005, 0.046) 0.013 0.007 (-0.008, 0.023) 0.371 0.022 (0.003, 0.040) 0.020 0.029 (0.008, 0.049) 0.006 a
  15-20 Ref   Ref   Ref   Ref  
  10-15 0.004 (-0.015, 0.023) 0.684 0.015 (0.001, 0.029) 0.040 -0.013 (-0.031, 0.007) 0.198 -0.018 (-0.038, 0.002) 0.082a
  ≤10 0.033 (0.008, 0.058) 0.009 0.033 (0.014, 0.051) <.001 -0.004 (-0.029, 0.022) 0.771 -0.010 (-0.038, 0.018) 0.481a
In the first four weeks
 Maximum temperature
  >30 Ref   Ref   Ref   Ref  
  25-30 0.007 (-0.020, 0.034) 0.593 0.008 (-0.012, 0.029) 0.427 -0.003 (-0.025, 0.020) 0.822 0.013 (-0.011, 0.036) 0.305a
  20-25 0.014 (-0.014, 0.042) 0.320 0.030 (0.009, 0.051) 0.006 -0.010 (-0.042, 0.022) 0.529 0.020 (-0.017, 0.056) 0.288a
  ≤20 0.054 (-0.041, 0.148) 0.265 0.037 (-0.034, 0.108) 0.310 -0.005 (-0.082, 0.072) 0.893 -0.008 (-0.086, 0.069) 0.833a
 Minimum temperature
  >20 0.035 (0.014, 0.055) 0.001 0.015 (-0.001, 0.030) 0.063 0.032 (0.014, 0.051) <.001 0.049 (0.026, 0.072) <.001 a
  15-20 Ref   Ref   Ref   Ref  
  10-15 0.007 (-0.012, 0.025) 0.470 0.018 (0.004, 0.032) 0.012 -0.010 (-0.031, 0.011) 0.338 -0.025 (-0.048, 0.001) 0.051a
  ≤10 0.062 (0.036, 0.088) <.001 0.056 (0.036, 0.075) <.001 0.017 (-0.015, 0.049) 0.302 -0.003 (-0.039, 0.033) 0.882a
In the last week
 Maximum temperature
  >30 Ref   Ref   Ref   Ref  
  25-30 0.019 (-0.007, 0.044) 0.148 -0.006 (-0.025, 0.013) 0.516 -0.003 (-0.022, 0.017) 0.796 0.009 (-0.012, 0.030) 0.412b
  20-25 0.006 (-0.020, 0.032) 0.669 -0.022 (-0.042, -0.002) 0.029 -0.013 (-0.042, 0.016) 0.380 0.003 (-0.028, 0.033) 0.866b
  ≤20 0.002 (-0.049, 0.053) 0.934 -0.043 (-0.082, -0.005) 0.029 -0.033 (-0.080, 0.013) 0.160 -0.025 (-0.073, 0.023) 0.302b
 Minimum temperature
  >20 -0.030 (-0.051, -0.009) 0.004 -0.010 (-0.025, 0.006) 0.223 -0.019 (-0.035, -0.002) 0.033 -0.042 (-0.061, -0.023) <.001 b
  15-20 Ref   Ref   Ref   Ref  
  10-15 -0.025 (-0.044, -0.007) 0.008 -0.024 (-0.038, -0.010) <.001 -0.014 (-0.036, 0.008) 0.221 -0.004 (-0.027, 0.019) 0.732b
  ≤10 -0.013 (-0.038, 0.012) 0.321 -0.023 (-0.042, -0.004) 0.019 -0.010 (-0.042, 0.022) 0.546 -0.005 (-0.038, 0.029) 0.777b
In the last four weeks
 Maximum temperature
  >30 Ref   Ref   Ref   Ref  
  25-30 -0.002 (-0.029, 0.025) 0.891 -0.010 (-0.030, 0.011) 0.345 -0.009 (-0.031, 0.012) 0.399 0.002 (-0.022, 0.025) 0.878b
  20-25 -0.014 (-0.042, 0.014) 0.338 -0.035 (-0.056, -0.014) 0.001 -0.038 (-0.070, -0.005) 0.024 -0.022 (-0.058, 0.014) 0.224b
  ≤20 -0.030 (-0.125, 0.066) 0.544 -0.038 (-0.110, 0.034) 0.302 -0.044 (-0.122, 0.033) 0.264 -0.031 (-0.110, 0.049) 0.449b
 Minimum temperature
  >20 -0.022 (-0.042, -0.002) 0.034 -0.002 (-0.017, 0.014) 0.815 -0.003 (-0.021, 0.014) 0.715 -0.030 (-0.052, -0.008) 0.007 b
  15-20 Ref   Ref   Ref   Ref  
  10-15 -0.028 (-0.046, -0.009) 0.003 -0.029 (-0.043, -0.016) <.001 -0.039 (-0.062, -0.016) 0.001 -0.024 (-0.050, 0.001) 0.061b
  ≤10 -0.021 (-0.047, -0.006) 0.008 -0.029 (-0.050, -0.008) 0.007 -0.043 (-0.078, -0.009) 0.014 -0.018 (-0.057, -0.004) 0.041 b
  1. Model 1: adjusted for maternal age at delivery, indigenous status, maternal marital status, mode of labor onset, parity, baby’s gender, and birth weight
  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